Answer: giros

AnswerCrossword Clue
GIROS

Copter sorts

GIROS

Copter predecessors

GIROS

Chopper precursors

GIROS
Early copters
GIROS
Copter ancestors
GIROSCopter relatives
GIROSHelicopter relatives
GIROSHelicopters.
GIROSTypes of aircraft.
GIROSEarly forms of helicopter.
GIROSAircraft.
GIROSCopters.
GIROSCopiers
GIROSRotating-wing craft
GIROSCopters' kin
GIROSCopter cousins
GIROSEarly whirlybirds