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Fast and Frequent Services by Air Routes for Correspondence Overseas


LOADING MAILS ON BOARD AN IMPERIAL AIRWAYS LINER at Croydon Airport. The mails are brought from London to the aerodrome in streamlined cars. These cars are painted blue, the colour chosen to distinguish air mail. Blue labels are used, where necessary, for affixing to air mail letters. Replies to correspondence may be received from distant countries in a few days by air mail, whereas the use of surface transport would require a lapse of several weeks before a letter was answered.

“THE P. & O. liner Strathnaver, carrying the last batch of sea-borne letters . . . left India on Saturday [February 26, 1938], closing a chapter in the history of mail transport.” In these words a London newspaper referred to the revolutionary change that the aeroplane and the flying boat have brought about in world communications.

The extent of the revolution which has taken place, and is taking place, in the overseas letter mail service may be gathered from an announcement of the British Post Office authorities: “Letters and postcards for most European countries prepaid at the ordinary international postage rates . . . are in general now forwarded by air or surface route, whichever offers the quicker delivery; and all letters and postcards for certain Empire countries . . . are forwarded by air in ordinary course. No air mail

label is required”. Not only do letters now reach their destination far more quickly than in former days, but the service is much more frequent. Moreover, this frequency and the speed of the air services enable a letter-writer to obtain a reply from his distant correspondent in a few days instead of weeks.

This speed of operation is not confined to letters and postcards. Air parcel services are in force to and from many European countries, the Customs clearance being specially expedited as a rule.

All mail operation calls for reliability, punctuality and speed, which have to be maintained despite handicaps of weather, climate and physical geography. Not until aviation had proved itself a reliable means of transport were the mails entrusted to it.

The history of the air mail is well worthy of study. In 1911 the British Post Office sanctioned an experimental air mail service between Hendon and Windsor, to mark the coronation year of King George V. Similar experimental services were operated in various other countries about this period. During the war of 1914-18 much official correspondence was carried by aircraft, and in May 1918 the first commercial air mail service was begun by the United States War Department between New York and Washington.

In Great Britain nearly a year elapsed between the signing of the Armistice on November 11, 1918, and the birth of the International Air Mail, which was officially inaugurated between London and Paris in November 1919. In the immediate post-war period, Royal Air Force machines had carried military mail between London and Paris and between Folkestone and Cologne, and before the official inauguration of the Post Office air mail, various experiments were made by the Post Office in cooperation with air transport companies. Mail was flown between London and France, Belgium and Holland, and also between London and Bristol, Birmingham, Newcastle-on-Tyne, Manchester and Glasgow.

A railway strike in September 1919 demonstrated to the public the resource of the postal authorities and the possibilities of trustworthy air mail operation. Fifty Royal Air Force machines carried a large quantity of mail between London and the chief towns in the provinces, every bag of mail being delivered successfully. In November of the same year it was announced that the Post Office had made arrangements for an air mail service between London and Paris. This may be said to have been the beginning of the international air mail services which now extend to the far corners of the Earth.

At first and for a number of years all letters intended for air transmission had to be prepaid at special air postage rates and special post boxes were erected in London and the larger provincial towns for air mail correspondence. Blue was chosen as the colour to distinguish air mail. Blue labels were issued for fixing to the envelopes of air mail letters and blue was adopted as the colour of the special air mail posting boxes.

To guide them in building up the service, the Post Office authorities took a number of censuses which gave interesting results. They found, for example, that 57 per cent of the outward air mail was posted in London, 18 per cent in twelve large cities and the remaining 25 per cent elsewhere. Following London in the list of heavy postings came Manchester, Liverpool, Glasgow, Birmingham and Edinburgh, after which there was a decline. Then came Newcastle-on-Tyne, Portsmouth, Bournemouth, Brighton, Hull, Bristol and Leeds.

Divided into “Roads”

The comparatively heavy postings at Portsmouth, Bournemouth and Brighton suggested that the officers, civil servants and others who had retired to these towns after years of service abroad were fully alive to the advantages of the air mail to keep in touch with friends overseas. By far the greater proportion of letters - 68 per cent -  were for countries on the Imperial air mail routes, 26 per cent were for European countries and 6 per cent for destinations in other parts of the world. From the beginning London was the hub of British air mail. An Air Mail Division of the London Foreign Section was formed to handle the outward air mails collected from London and from all parts of Great Britain and Northern Ireland, so that all such mail, wherever posted, could be brought to the same point.

It was arranged that air mail posted in the provinces should be tied to the letter bill accompanying each mail, made up into separate bundles or included in an enclosure bag, according to the quantity of correspondence. The object was to ensure that the air mail came under immediate notice directly the mail was opened, and it was transferred to the Air Mail Division in London at once. Mail collected in London from the ordinary posting boxes or from the blue boxes was brought to the same point.

The Air Mail Division was divided into sections called “roads”, each road being for one country or for a group of neighbouring countries. The first stage was to sort the mail and to transfer it to the correct “road”, and the next stage to sort the individual mails.


THE AIR LINER HANNIBAL AT ENTEBBE, UGANDA. Machines of this type have been extensively used in the development of British air mail services. First-class mail (letters, letter packets and postcards) is now sent by air to Uganda and many other Empire destinations as the normal means of transmission. This exemplifies the revolution that the aeroplane has brought about in world communications.

Separate mails were sent out for most of the stopping places on the main air routes, as well as for other destinations. Correspondence for places not on the main air routes had to be sorted according to the facilities of the air, railway or ship connexions. This involved up-to-the-minute knowledge of the changing conditions of transport all along the air routes, for it sometimes happened that the airport nearest in geographical distance to the destination of the letter was not nearest in time of transit, as the feeder service from another airport was quicker.

Advantage was taken of the facts that the collection and sorting of the mail were concentrated in London, and that the direct air mail services left from Croydon Airport. Many arrangements had to be made quickly, or unexpected difficulties had to be surmounted, and the proximity of the two centres enabled matters to be arranged promptly.

The chief problem in short air mail services, such as that between London and Paris, is the time taken by the surface connexions between post offices and airports at either end of the route. Although this time-lag is not serious in long-distance air mail, because it diminishes in proportion to the length of the air route, it is an obstacle to the expediting of short air routes when it is sometimes greater than the time of the air journey.

During tests made in London it was found that an interval of thirty minutes had to be allowed from the time the air mail box at the head post office in King Edward Street, E.C.1, was cleared to the moment when the van carrying the mail to Croydon was due to leave, and that forty-five minutes had to be allowed for heavy mails posted for the Imperial routes. The time of transport to Croydon by motor vehicle or by van was scheduled at fifty minutes, and a further ten minutes were required for weighing and placing the mailbags in the aeroplane. Thus the total time which elapsed between posting and the departure of the aeroplane was from an hour and a half to an hour and three-quarters.

Origin of Imperial Airways

There was a similar interval between the landing of the aeroplane at Le Bourget and the arrival of the mail at the distributing office in Paris. Moreover, the letters, unless prepaid for express delivery, had to await the beginning of a scheduled delivery.

With the continuous development of aviation, air transport has come more and more to be regarded as an ordinary, and not an extraordinary, means of postal transmission. With the extension of the arrangements under which letters and postcards for most European countries and for certain Empire countries on the England-Africa and England-India-Malaya air routes are sent by air as a normal means of transmission, there has been a steady decrease in the number of services requiring special treatment in the way of prepayment of special air postage, the affixing of blue labels, posting in the special blue boxes or segregation before the mail is sent to London.

At the present time all first-class mail (letters, letter packets and postcards) for all parts of Europe except Spain, Portugal, Gibraltar and Malta, prepaid at the ordinary international postage rates, is in general sent by air, if this affords quicker delivery than surface routes, without the necessity for any special action on the part of the correspondent. Mail is now being sent by air to European countries under these arrangements at the rate of about 650 tons a year.

ARMSTRONG WHITWORTH ENSIGN, built for carrying mails and passengers on parts of the Empire air routes

ARMSTRONG WHITWORTH ENSIGN, built for carrying mails and passengers on those parts of the Empire air routes which are more suited to landplanes than seaplanes. The Ensign was designed to carry 7,200 lb. of mail as well as passengers, and to have a top speed of 200 miles an hour, with a cruising speed of 160 miles an hour. The engines chosen were 880 horse-power, moderately supercharged Armstrong Siddeley Tiger IXs.

Before an account is given of the working of the Empire Air Mail Scheme, reference may be made to the origin of Imperial Airways, the organization entrusted with the operation of this great project, and to the stages in the development of its services.

When the air mail service between London and the Continent was begun, the companies operated at a loss, one cause being that foreign countries subsidized. air mail machines landing in Great Britain. After many vicissitudes, including one short period when British civil aviation was suspended, a Government Committee was set up to examine the feasibility of an Imperial air mail service and on April 1, 1924, Imperial Airways was formed by the amalgamation of four companies: Handley Page Transport Ltd, Instone Air Line Ltd, Daimler Airways Ltd, and British Marine Air Navigation Co., Ltd.

At first services were restricted to Europe, because the machines of that time were not suitable for reliable operation on the Imperial routes and reliability was essential.

An air service between Cairo, Egypt, and Basra, Iraq, was one early link in the services, which were extended until they reached India, in March 1929. The England to East Africa air mail was inaugurated in February 1931, with an extension to South Africa in January 1932. The England to India route was extended to Malaya in December 1933, and to Australia in December 1934.

The period 1935-37 saw the duplication of the services on the main trunk routes to South Africa and Australia, and the introduction of feeder services to Hong Kong from Penang and to Nigeria and the Gold Coast from Khartoum.

In June 1937 the first stage of the Empire Air Mail Scheme was introduced on the route to South Africa. This scheme provided for the sending by air as the normal means of transmission of the whole of the first-class mail for Empire countries on the England- South Africa and the England-India Australia air routes, and for Egypt, at a flat postage rate of 1½d. per half ounce for letters and letter packets and 1d. for postcards.

The second stage of the scheme was introduced on the route to India, Burma and Malaya in February 1938.

To Singapore in Ten Days

With these two stages of the Empire Air Mail Scheme in operation, first-class mail is now sent by air as the normal means of transmission at a flat postage rate to the following destinations: Aden, Anglo-Egyptian Sudan, Bahrein, Burma, Ceylon, Egypt, India, Kenya, Malay States, Mauritius, North Borneo, Northern Rhodesia, Nyasaland, Palestine, Sarawak, Seychelles, Southern Rhodesia, Straits Settlements, Tanganyika Territory, Tibet, Transjordan, Uganda, Union of South Africa and Zanzibar.

The third and last stage of the scheme was scheduled to come into operation in 1938, the intention being to extend these arrangements to Hong Kong, Australia and New Zealand. There are seven postal services a week to Egypt, four a week to Calcutta and two to Malaya, compared with the previous surface service of one post a week to most Oriental countries. Letters are delivered in Alexandria in three or four days, compared with from four to six days by the old method; in Calcutta in about a week instead of sixteen days, and in Singapore in about ten instead of twenty-two days.

Long-distance travel by air is expensive at present for those of limited means, but the air mail has been developed to provide speedy communication by letter for all. The modest number of 212,380 letters carried by Imperial Airways in its first year increased to 34 million letters in 1936, and then expanded enormously with the change from surface to air transport for all letters for countries embraced in the Empire Air Mail Scheme.


CASTOR, ONE OF THE EMPIRE FLYING BOATS, being loaded at Hythe, Southampton Water. Flying boats have special advantages over landplanes on many of the Empire routes. Petrol is often much cheaper at ports than at inland places. The use of large landplanes over certain stretches of country would call for the provision of new aerodromes and hangars which would be expensive to build.

The two main Empire air routes from England proceed via France, Italy and Greece to Alexandria, where they diverge. The Eastern Route is by way of Palestine, Baghdad and the Persian Gulf to Karachi, which is the junction for various feeder services in India. From Karachi an Indian company operates in conjunction with Imperial Airways, and the mail is carried via Jodhpore, Delhi, Cawnpore and Allahabad to Calcutta, and from there by way of Burma (Akyab and Rangoon), Siam (Bangkok), and Malaya (Penang) to Singapore. Singapore is the junction for Australia, and an Australian company associated with Imperial Airways carries the mail via the Netherlands East Indies to Darwin, Australia. From Darwin the route is through Queensland via Longreach and Charleville to Brisbane. Other Australian services run in connexion.

The Southern Route is from Alexandria to Cairo, and thence through Egypt to Khartoum (Sudan), Port Bell (Uganda), Kisumu and Mombasa (Kenya), Dar-es-Salaam (Tanganyika), Beira and Lourenjo Marques (Portuguese East Africa), and on to Durban, the terminal point of the service. Feeder services operate from Kisumu to Nairobi (Kenya) and from Beira to Salisbury (Southern Rhodesia), Blantyre (Nyasa-land) and Lusaka (Northern Rhodesia).

The great length of the routes - that from London to Brisbane being 12,780 miles, and that from London to Durban is 7,300 - presented difficulties complicated by the wide variety of climate, geography, races and political conditions of the various countries traversed. The establishment of a schedule for air mail was therefore extremely complicated in every way, and the survey flights and ground organization required time.

From the beginning the great aim was to establish the air mail, and not merely to provide passenger transport, although the requirements of passengers were studied closely. Experience showed that large machines were essential for the economical development of the air mail, but the peculiarities of the routes did not enable the problem to be solved by merely increasing the size of the machines.

In Europe and in America the trunk routes link cities which are centres of industrial civilization, but this does not apply to the greater part of the routes on the Imperial lines, which pass over countries where transport is slow and costly in the interior. Although large landplanes were available, the cost of providing fuel and accommodation for them had to be considered.

One factor was that fuel alone cost twice as much at certain inland places on the routes as at ports on the coast of the same country. Another was the fact that some places were subjected to torrential rain and gales at certain seasons and were remote from supplies of material required for building adequate aerodromes or for sheltering large machines during gales. Yet another factor was the cost of remodelling existing aerodromes.

To certain problems the flying boat has provided the solution, as it has some advantages over the large landplane. Provided that the moorings are adequate, a moored flying boat will swing into the wind during a gale and will ride out the storm without requiring special housing.

The development of four-engined machines able to fly on the normal power output of three of their engines showed that no more risk was taken in flying four-engined flying boats over land than in flying four-engined landplanes over water. Provision of tenders for flying boats and the carriage to shore of mail and passengers had to be considered, but no insuperable difficulties were involved.

It was not possible to concentrate entirely on flying boats, as part of the Eastern Route was more suitable for landplanes. The solution was to provide large landplanes for the land stages, existing aerodromes being improved and new ones built; and to provide flying boats for the appropriate routes, with marine airports and surface craft to act as tenders.

A STOP AT M'BEYA IN TANGANYIKA TERRITORY on the South African air mail route. The aircraft is the Atalanta, the first of the A.W. 15 type machines built by Armstrong Whitworth specially for use in tropical climates. The undercarriage is of low-drag type, the major part of it being accommodated inside the fuselage. The four Armstrong Siddeley Serval engines are of 340 horse-power each.

To meet the requirements of air mail expansion, two types of machine were designed, the Ensign for landplanes and the Empire for flying boats. Each represented the best of its class. Both were high-wing all-metal monoplanes. When the decision was made to concentrate upon two types, fourteen Ensign landplanes and twenty-eight Empire flying boats were ordered.

The Ensigns were designed to carry about 7,200 lb of mail, in addition to passengers, and were powered by four Armstrong Siddeley Tiger IX engines, each of which developed 880 horse-power. Cruising speed was about 160 miles an hour, top speed 200 miles an hour and range about 500 miles against a head-wind of 40 miles an hour. The Empire flying boats were powered by four Bristol Pegasus X.C. engines, each of 740 horsepower. Cruising speed was 164 miles an hour and top speed 200 miles an hour. The mail capacity was 6,200 lb.

For the landplanes landing fields were prepared at intervals of about 500 miles and existing aerodromes were improved. To facilitate day and night navigation a network of weather and radio stations was instituted.

For the flying boats many new surface craft had to be ordered. Some of these craft were, in effect, control towers, being equipped with radio and signalling apparatus to control all flying boats in the marine airport to which each was assigned. Special types of moorings and floating flares were designed.

At some remote places the charts were not up to date and surveys had to be made to ensure that there was enough water at all stages of the tides to enable flying boats to take off and to alight, and also to be moored without the risk of going aground at low water.

A type of raft was designed to form a small dock within which mail and passengers could be disembarked to port and starboard of the flying boat simultaneously. The raft was connected with the shore by floating gangways. In addition to swift launches for ferrying mails and passengers between shore and flying boat, fuel launches were built. These were designed to pump more than a ton and a half of petrol into the tanks of a flying boat in little more than five minutes.

The success of years of operation of mail routes was such that, apart from passengers, Imperial Airways had to plan for a great increase in mails. As late as 1936 the total ton-miles flown on the Empire services was less than four million, but future requirements needed provision for carrying at least fourteen million ton-miles of mail, apart from the weight of the passengers and the crew.

It was considered that, apart from the increase of mails at Christmas, plans would have to be prepared for an annual total of about 2,000,000 lb. of mail between Great Britain, India and Burma; and further, that additional mail between Great Britain, Malaya, Hong Kong and Australia would bring the total to about 3,500,000 lb. On the Africa routes the amount of mail carried in both directions was estimated at about 1,000,000 lb. It was expected that at Christmas time the entire fleet, supplemented by additional aircraft, would be kept working day and night, backwards and forwards, for a period of five weeks.

At the present time the following air services are provided each week in either direction, from and to London: Egypt (Alexandria) seven services; Central Africa (Kisumu) three; South Africa (Durban) two; India (Calcutta) four; Malaya (Singapore) and Australia (Sydney) two. The Empire Air Mail scheme in its complete form envisages additional air services to Egypt, India and Australia. Further, it is hoped eventually to reduce the time of transit thus: Egypt two days, India three days, Central Africa three days, Durban four and a half days, Singapore four and a half days, Australia seven days.

The arrangements for the use of the air in the ordinary course for first-class mail to Empire and European destinations have greatly reduced the number of air mail services for which it is still necessary to pay a special air postage charge and to make use of the special blue air mail label.

Establishment of the North Atlantic air mail is the next important step in development, and steady progress had been achieved by 1938.

Within Great Britain and Northern Ireland the distances are short and the surface transport efficient; yet, during 1937, about 500 tons of letter mails were conveyed by air.

The Scylla was a development of the Kent type of flying boat used by Imperial Airways

USED ON THE LONDON PARIS route of Imperial Airways, the Scylla was a development of the Kent type of flying boat used by Imperial Airways in the Mediterranean. The Kent flying boat was designed in 1931, and the Scylla was produced about three years later. The machine has a span of 113 feet, is just over 86 feet long and has a fully laden weight of 33,000 lb.

You can read more on “Advance of the Empire Air Mail”, “Cobham’s Pioneer Empire Flights” and “Singapore’s Great Airport” on this website.

You can read more on “Handling the Overseas Mail” in Shipping Wonders of the World, and on “Travelling Post Offices” in Railway Wonders of the World

Air Mails of the Empire