When the sequence reached the prefix K it was decided to start at K for all subsequent letters instead of K1. Bythe first sequence had reachedand it was decided to start an alpha-numeric system from A1 allocated to a Royal Aircraft Factory BE. The first registration number was allocated to a Short S. This first series ran from 1 to with blocks allocated to each service. In an RAF or FAA pilot's personal service log bookthe registration number of any aircraft flown, along with any other particulars, such as aircraft type, flight duration, purpose of flight, etc.

The registration numbers are allocated at the time the contract for supply is placed with the aircraft manufacturer or supplier. The prefix 'A' was allocated to balloons of No. Military aircraft operated by government agencies and civilian contractors for example QinetiQ are also assigned registration numbers from this system. All UK military aircraft are allocated and display a unique registration number.

United Kingdom military aircraft serial numbers are aircraft registration numbers used to identify individual military aircraft in the United Kingdom UK.

Raf squadron codes and serial numbers