 The series ' title was derived from a letter written by Gerry 's brother , Lionel , while he had been serving overseas as an RAF flight sergeant during World War II . While stationed in Arizona , Lionel had made reference to Thunderbird Field , a nearby United States Army Air Forces base . Drawn to the " <unk> " of " Thunderbirds " , Anderson dropped his working title of " International Rescue " and renamed both the series and IR 's rescue vehicles , which had previously been designated <unk> 1 to 5 . His inspiration for the launch sequences of Thunderbirds 1 , 2 and 3 originated from contemporary United States Air Force launch procedure : Anderson had learnt how the Strategic Air Command would keep its pilots on permanent standby , seated in the <unk> of their aircraft and ready for take @-@ off at a moment 's notice . 
