Answer: fortresses

AnswerCrossword Clue
FORTRESSESU. S. bombing planes.
FORTRESSESThey wing their way to Victory.
FORTRESSESFlying ....
FORTRESSESStrongholds.
FORTRESSESStrongholds
fortressesA person or thing not susceptible to outside influence or disturbance
fortressesA heavily protected and impenetrable building
fortressesA military stronghold, esp. a strongly fortified town fit for a large garrison