Bell is offering a next-generation tilt-rotor, V-280, evolved from its V-22 Osprey, which tilts its huge rotor blades between vertical and horizontal positions to gain both the best features of a helicopter (vertical takeoff and landing) and those of a propeller plane (fuel-efficient speed for long range flight). The Sikorsky-Boeing Defiant looks more like a traditional helicopter, but is based on Sikorsky's "X2" technique of combining two counter-rotating rotors, one on top of the other, with a pusher propeller at the tail.