The title flight officer was a military rank used by the United States Army Air Forces during World War II, and also an air force rank in several Commonwealth countries, where it was used for female officers and was equivalent to the rank of flight lieutenant. The term flight officer is sometimes used today to describe job title positions as aircrew members.

Flight lieutenant is a junior officer rank used by some air forces, with origins from the Royal Air Force. The rank originated in the Royal Naval Air Service (RNAS) in 1914. It fell into abeyance when the RNAS merged with the Royal Flying Corps during the First World War but was revived in 1919 in the post-war RAF. The rank is used by air forces of many countries that have historical British influence.