 Set between <unk> and <unk> , Thunderbirds follows the exploits of the Tracy family , headed by American ex @-@ astronaut turned multi @-@ millionaire philanthropist Jeff Tracy . He is a widower with five adult sons : Scott , John , Virgil , Gordon and Alan . The Tracys form International Rescue ( IR ) , a secret organisation dedicated to saving human life . They are aided in this mission by technologically advanced land , sea , air and space vehicles , which are called into service when conventional rescue techniques prove ineffective . The most important of these are five machines named the " Thunderbirds " , each assigned to one of the five Tracy brothers : 
