The earliest known international airmail cover from North Borneo

This cover is earlier than the dates recorded by Proud and Robson Lowe of  July 1932 and 2 November 1931 respectively. It was sent soon after after the issuance of the 1931 50th Anniversary adhesives. 

The post date was 30 March 1931 with transit cds of Singapore 6 Ap 1931 and Penang 7 Ap 1931. It was franked to a total of 28c with three very attractive 1931 Anniversary stamps but underpaid for registration purposes. It bears the Sandakan N Reg label for 1931 as well as a normal By Air Mail/Par Avion label. It also has the very uncommonly seen use the AIR MAIL to INDIA label on cover. At the very top, there is the typed instruction, BY AIR MAIL via Karachi-London  route.

Being one of the very first letters to be sent by mail from North Borneo, the postal clerk at Sandakan probably had not received the exact rates yet. The airmail rate should have been 6c Imperial rate for the first oz, 12c registration and an Air Fee of 20c which gave a total of 38c. It was underpaid by 10c and was treated as ordinary mail in Britain and hence there was no arrival registration GB backstamp. 

The journey would have started with boat to Singapore, train to Penang, boat to India, overland by train to Karachi before being flown by stages to arrive at Croydon near London. Croydon was the world's first international airport, built 1928 and closed down in 1959. In the month after this cover, Imperial Airways started flying from London to Darwin in Australia.  

The British North Borneo Herald issue of 17 August 1931 has the following interesting article on page 148:

MAGIC OF THE AIR-MAIL. ENGLAND TO INDIA IN FIVE DAYS.

By HARRY HARPER

An experience to linger in one's memory is to fly as a passenger over that great air-mail route which is operated by Imperial Airways between England and India. By the accelerated time schedule which will be in operation this summer, one will ascend from London on Saturday morning and be in India on the following Thursday, having flown 5,000 miles above land and sea, with panoramas which will enthrall you unfolding themselves beneath your outlook window.

It seems more like magic than reality to be able to leave London on Saturday morning and to be in Alexandria on the following Monday; to alight at Baghdad on Tuesday evening; and to reach India by Thursday afternoon. Yet such apparent miracles as these, the fruit of organisation and of operating experience, are now being accomplished regularly as a matter of daily routine.

Passengers bound for India by air assemble on Saturday morning at Airways House, London. Then, after your passports have been examined and your luggage taken charge of by airway porters, you are escorted to waiting ears and driven to the air-station at Croydon. Taking your armchair seat in one of the powerful Armstrong Siddeley passenger-planes of Imperial Airways, you ascend at 8.30 a.m. and sweep over Kent to the sea-coast, passing swiftly above the Channel on your way to Paris.

After a brief halt at Le Bourget, the Paris airport, your pilot steers for Basle, beautiful views lying below, a panorama of mighty mountains and fertile valleys. Then the city of Basle, where the Rhine makes an almost right-angle turn, is reached. On the east side of the city lies the aerodrome, where at four o'clock on Saturday afternoon your air express alights.

Now, for a brief spell, you desert airway for railway, taking your place in a sleeping-car train and travelling, throughout the night to Genoa, which you reach on Sunday morning. At Genoa you find awaiting you one of the powerful multi-engined flying-boats of Imperial Airways. In this, on Sunday morning, you ascend and fly down the Italian coast via Naples to Corfu, where you alight that same evening.

Early on Monday morning you are on the wing again, steering for Athens and Crete, with wonderful views below, and on above the Mediterranean to Alexandria, where you alight at 4.30 p.m. on Monday afternoon, the seaplane base being only a short distance from the Royal Palace of Ras-el-Tin. Changing again from flying-boat to aeroplane, you obtain a fascinating glimpse of Cairo, while after this comes a wonderful aerial view of the Suez Canal. From your lofty view-point you can see not only the end of the Canal at Port Said, but also the other end in the Gulf of Suez.

Soon your "magic carpet" has carried you over the Sinai desert to Gaza. On again, fresh wonders greet you, the roundtopped hills of Judah ; Bethlehem on your left; and Jerusalem on a hill beyond. Then you have an impressive, swiftly-glimpsed panorama of the Dead Sea which, it has been said, "looks like the bottom of the world" when viewed from a height of about 5,000 feet. From here you pass to Rutbah Wells, romantic desert station, and on towards Baghdad, crossing above the river Euphrates. Soon after this you find yourself over Baghdad, " Jewel of the East " , and as you glide down you catch a passing glimpse of the golden domes of the Kad-i-Main Mosque, and of the narrow streets and date gardens of the city.

Early on Wednesday morning you are in the air again, passing over that wonderful Arch of Ctesiphon and approaching the legendary site of the garden of Eden. After this, from Basra on to Bushire, you see a transition from the tropical basin of the river system to the volcanic mountain-ranges of Persia. Flying via Lingeh, you reach and alight on Wednesday evening at Jask, where there is a cable and telegraph station of the Indo-European Telegraph Company.

Ascending again on Thursday, you pass high above mountains and vast stretches of sand. Then, presently, you find yourself nearing the harbour and port of Karachi. Your air express passes to the north of the town, and on to the commercial air station which lies inland. It is at  3.30 pm on Thursday that your air express glides down at Karachi. You have flown from England to India in exactly 5 days 2 hours 35 minutes. A hundred years ago it was thought wonderful when one of the old sailing ships made a voyage between England and India in not more than 91 days, Five days as compared with ninety-one days ! Or, to contrast the aerial mail with the fastest existing surface transport, 5 days as compared with 15 days. Such apparent miracles are possible only with the modern aircraft, which wings its way unhindered above sea, mountains, forests, or deserts. On Friday morning the air-mail goes on via Hyderabad and Jodhpur to Delhi, reaching there at 2.40 p.m. So your aerial journey ends. You have seen the world from the new and fascinating view point of the traveller who flies, and you have enjoyed a personal experience which will convince you, if you need convincing, that the long-distance travel of the future must leave the surface of land and sea and make its swift progress through the air.

London-Paris-Basle-Genoa-Corfu-Alexandria-Baghdad-Jask-Karachi route which can be traced on the map below.

Armstrong Whitworth biplane powered by 3 Sidderley "Jaguar" engines for the first part of the journey from Croydon to Genoa - Imperial Airways archives.

Short Brothers S17 Kent four engine flying boat which can accommodate 15 passengers for the journey from Genoa to Alexandria.