Boeing Vertical Lift is a strategic business unit within Boeing Defense, Space & Security (BDS) specializing in the design, production, and support of rotorcraft. It is one of the world's largest manufacturers of military helicopters, maintaining a global fleet of attack and heavy-lift aircraft. The division is headquartered in Ridley Park, Pennsylvania, at a facility that has been a center for rotorcraft innovation since the Piasecki/Vertol era.