It has a NATO ranking code of OF-1 and is equivalent to a lieutenant in the British Army or the Royal Marines. However, it is superior to the nearest equivalent rank of sub-lieutenant in the Royal Navy.
The equivalent rank in the Women's Auxiliary Air Force was "section officer".
The term "flying officer" was originally used in the Royal Flying Corps as a flying appointment for junior officers, not a rank.
On 1 April 1918, the newly created RAF adopted its officer rank titles from the British Army, with Royal Naval Air Service sub-lieutenants (entitled flight sub-lieutenants) and Royal Flying Corps lieutenants becoming lieutenants in the RAF. However, with the creation of the RAF's own rank structure on 1 August 1919, RAF lieutenants were re-titled flying officers, a rank which has been in continuous use ever since.
The rank title does not imply that an officer in the rank of flying officer flies an aircraft. Some flying officers are aircrew, but many are ground branch officers. Amongst the ground branches some flying officers have command of flights.