The Credit of Longest Air Race goes to MacRobertson Air Race from Mildenhall England to Melbourne Australia in 1934. This race is also known as the London to Melbourne Air Race. The crew of a de Havilland took a time of 70 hours and 54 minutes to win the race. The race was a part of the Melbourne Centenary celebrations that took place in October, 1934. The idea of the race was devised by the Lord Mayor of Melbourne. Sir Macpherson Robertson, a wealthy Australian confectionery manufacturer, put up a prize fund of $75,000 on the conditions that the race be named after his MacRobertson confectionary company. He also made sure that it be organised to be as safe as possible.

The race organised by the Royal Aero Club would run over an 11,300 mile course. There was no limits to aircraft size, power or crew but it was made compulsory by the organisers that aircrafts must carry three days' rations per crew member, floats, smoke signals and efficient instruments. The race was divided into a speed competition and a handicap division. There were prizes for the best performance on a handicap formula by any aircraft finishing within 16 days and the outright fastest aircraft. Initially, there were 64 entrants from 13 countries, but when the race started on 20 October 1934, the field had been reduced to 20 planes from seven countries. These planes includes a mixture of earlier racers, light transports, old bombers, two new generation of american all-mtal passengers transports and three purpose built de Havilland DH.88 comet racers. The route stretched over 19 countries and seven seas. Five compulsory stops were designated for both divisions. Between the five stops (Baghdad, Allahabad, Singapore, Darwin and Charleville) pilots could select their own route. Eleven finished the course. Three aircraft crashed, in one case killing both crew.

MacRobertson Air Race

Jim and Amy Mollison, in the Comet Black Magic, were first off the line but they were forced to retire at allahabad due to engine trouble. This left the eventual winners of the speed division, British fliers C.W.A. Scott and T. Campbell Black in a red DeHavilland 88 Comet, named Grosvenor House, well ahead of the field. They reached Melbourne in two days, 23 hours, 18 seconds,despite flying the last stage with one engine throttled back because of an oil-pressure indicator giving a faulty low reading. There was a race rule that no aircraft can win more than one prize otherwise the Grosvenor House would have won the Handicap prize as well.

The de Havilland DH.88 Comet was a twin-engined British aircraft. It was specifically designed for the MacRobertson Air Race. Three examples of these planes took part in the race and one of them won. It set many aviation records during the race and afterwards, as a pioneer mail plane. The clean lines of the DH.88, especially in the striking colours of Grosvenor House, make it a true design classic. The unit cost was £5,000.