Flight lieutenant (Flt Lt in the RAF and IAF; FLTLT in the RAAF and RNZAF, formerly sometimes F/L in all services) is a junior commissioned rank which originated in the Royal Naval Air Service and continues to be used in the Royal Air Force. The rank is also used by the air forces of many countries which have historical British influence, including many Commonwealth countries, and it is sometimes used as the English translation of an equivalent rank in countries which have a non-English air force-specific rank structure. It ranks above flying officer and immediately below squadron leader. The name of the rank is the complete phrase; it is never shortened to "lieutenant". In RAF informal usage, a flight lieutenant is sometimes referred to as a "flight lieuy".
The equivalent rank in the Women's Auxiliary Air Force (WAAF), Women's Royal Air Force (WRAF) (until 1968) and Princess Mary's Royal Air Force Nursing Service (PMRAFNS) (until 1980) was flight officer.
On 1 April 1918, the newly created RAF adopted its officer rank titles from the British Army, with Royal Naval Air Service lieutenants (entitled flight lieutenants and flight commanders) and Royal Flying Corps captains becoming captains in the RAF. In response to the proposal that the RAF should use its own rank titles, it was suggested that the RAF might use the Royal Navy's officer ranks, with the word "air" inserted before the naval rank title. For example, the current rank of flight lieutenant would have been "air lieutenant". Although the Admiralty objected to this simple modification of their rank titles, it was agreed that the RAF might base many of its officer rank titles on navy officer ranks with differing pre-modifying terms. It was also suggested that RAF captains might be entitled flight-leaders. However, the rank title flight lieutenant was chosen as flights were typically commanded by RAF captains and the term flight lieutenant had been used in the Royal Naval Air Service. The rank of flight lieutenant has been used continuously since 1 August 1919.
Although in the early years of the RAF a flight lieutenant commanded an aircraft flight, it is rare that a flight lieutenant is in command of a flying unit in the modern air force. Instead, aircrew flight lieutenants are typically experienced pilots (or weapons system officers) without command of other personnel. However, ground flights which are administrative sub-divisions of squadrons are ordinarily commanded by flight lieutenants and these can range in size from a few specialist non-commissioned personnel to 50 or more personnel for engineering or other manpower intensive roles. In the Air Training Corps, a flight lieutenant is usually the officer commanding of a squadron. Retired flight lieutenants are the first rank that may continue to use their rank after they have left active service.
The rank insignia consists of two narrow blue bands on slightly wider black bands. This is worn on both the lower sleeves of the tunic or on the shoulders of the flight suit or the casual uniform. The rank insignia on the mess uniform is similar to the naval pattern, being two band of gold running around each cuff but without the Royal Navy's loop. Unlike senior RAF officers, flight lieutenants are not entitled to fly a command flag under any circumstances.
Other air forces 
The rank of flight lieutenant is also used in a number of the air forces in the Commonwealth, including the Bangladesh Air Force, Ghana Air Force, Indian Air Force, Pakistan Air Force, Royal Australian Air Force and Royal New Zealand Air Force. It is also used in the Egyptian Air Force, Hellenic Air Force, Royal Air Force of Oman, Royal Thai Air Force and the Air Force of Zimbabwe.
The Royal Canadian Air Force used the rank until 1968, when the three armed services were unified and army-type ranks were adopted; flight lieutenants became captains. In official French Canadian usage, a flight lieutenant's rank title was capitaine d'aviation.
Up until the late 1970s, the Royal Malaysian Air Force used the rank. Thereafter the rank of captain was used instead.
An RAAF flight lieutenant's sleeve/shoulder insignia
A RTAF flight lieutenant's rank insignia
A PAF flight-lieutenant's rank insignia.
Notable flight lieutenants 
- Gough Whitlam, Prime Minister of Australia (1972-1975).
- Jerry Rawlings, Ghanaian politician who twice served as his country's president.
- Donald Pleasance, British actor.
- Sir Patrick Moore, British astronomer.
- Sir Arthur C. Clarke, British author and inventor.
- Sir Christopher Lee, British actor, served in RAF Intelligence during World War II.
- Prince William, Duke of Cambridge (heir to the British throne).
- Rory Underwood, Leicester, England and British and Irish Lions winger
See also 
- "Ranks and Badges of the Royal Air Force". Royal Air Force. 2007. Retrieved 2007-12-01.
- The London Gazette: . 6 January 2009. Retrieved 2009-01-18.
|Commissioned officer ranks of the British Armed Forces|
|NATO rank code||Student Officer||OF-1||OF-2||OF-3||OF-4||OF-5||OF-6
|Royal Navy||O Cdt||Mid||SLt||Lt||Lt Cdr||Cdr||Capt||Cdre||RAdm
|Adm of the Fleet|
|Royal Marines||2Lt||Lt||Capt||Maj||Lt Col||Col||Brig||Maj-Gen||Lt-Gen||Gen
|Army||O Cdt||2Lt||Lt||Capt||Maj||Lt Col||Col||Brig||Maj-Gen||Lt-Gen||Gen
|Royal Air Force||OC / SO||APO / Plt Off||Fg Off||Flt Lt||Sqn Ldr||Wg Cdr||Gp Capt||Air Cdre||AVM||Air Mshl||Air Chf Mshl