Skunk Works is an official pseudonym for Lockheed Martin's Advanced Development Programs (ADP). The program was formerly called Lockheed Advanced Development Projects. It is in charge of a few aircraft type designs. These includes the U-2, the Lockheed SR-71 Blackbird, the Lockheed F-117 Nighthawk, Lockheed Martin F-22 Raptor, and the Lockheed Martin F-35 Lightning II. These aircrafts are used in several countries' air forces.