The Royal Air Force Ensign is the official flag which is used to represent the Royal Air Force. The Ensign has a field of air force blue with the Union Flag in the canton and the Royal Air Force roundel in the middle of the fly. Ever since the formation of the RAF in 1918, the Air Council wanted to introduce a flag which would be flown at RAF stations. However, the Admiralty had the right to veto the introduction of any new flag that was to be flown within the British Empire or on a British vessel.
Although the Admiralty were initially opposed to granting the RAF its own flag, after considerable pressure from the Air Council, they reluctantly agreed to the introduction of such a flag, stating that the Air Force should adopt the Union Flag defaced with a suitable device. The Air Council did not welcome the Admiralty's condition as they wished to use the White Ensign with the St George's Cross removed. Whilst the War Office had no objections to this proposed design, the Admiralty certainly did and they rejected the Air Council's suggestion on the basis that the White Ensign was exclusively reserved for Royal Navy use.
The Air Council then submitted a design featuring a jack with a white border, but the Admiralty rejected this submission as it was the already in use as the signal to summon a ship's pilot. The Air Council then re-submitted the original design which, unsurprisingly, was rejected once again. When the situation came to the attention of King George V, he suggested that the matter be referred to the Cabinet.
Although papers were drafted, the question was never debated in Cabinet. The dispute soon became more widely known and various designs were suggested by members of the public. Although none of these suggestions were accepted, the idea that the Roundel (which had been used by both the Royal Flying Corps and the Royal Naval Air Service) might be adopted was viewed favourably by senior RAF commanders. Air Vice Marshal Sir John Salmond suggested that the Union Flag be placed in the canton in order that the design carry the mark of British authority.
The Air Council subsequently agreed upon the design in use today as their preferred option. The Chief of the Air Staff, Air Marshal Sir Hugh Trenchard, then brought the design before King George V who approved the design. The design was then sent to the Admiralty and it was accepted as an Ensign in December 1920. On March 24, 1921, the King signed an Order in Council ratifying its use..