as its p-51 mustangs and p-47 thunderbolts became more and more obsolescent in the jet age of the 1950s, the force structure gradually changed to include a significant number of airlift, tanker, and specialized combat-support units. as the air national guard expanded, additional squadrons, including airlift units as well as air resupply and communications units, were established. additional command and control groups and wings were also established by the national guard bureau and allocated to the states. the ang however, unlike the active duty usaf, did not inactivate its combat groups during the 1950s as part of the tri-deputate organization. many of the combat groups remained assigned to the wings from which they were derived. it wasn't until 1974 that the ang fully adapted the usaf tri-deputate organization and inactivated its combat groups, assigning its operational squadrons directly to the wings.