The Lockheed Martin F-35 Lightning II is a family of single-seat, single-engine, all-weather stealth multirole fighters undergoing final development and testing by the United States. The fifth generation combat aircraft is designed to perform ground attack, aerial reconnaissance, and air defense missions. The F-35 has three main models: the F-35A conventional takeoff and landing (CTOL) variant, the F-35B short take-off and vertical-landing (STOVL) variant, and the F-35C carrier-based Catapult Assisted Take-Off But Arrested Recovery (CATOBAR) variant. On 31 July 2015, the first squadron was declared ready for deployment after intensive testing by the United States.[14][15]