Pegasus is an air-launched launch vehicle developed by Orbital Sciences Corporation (OSC) and now built and launched by Northrop Grumman. Capable of carrying small payloads of up to 443 kg (977 lb) into low Earth orbit, Pegasus first flew in 1990 and remains active as of 2021. The vehicle consists of three solid propellant stages and an optional monopropellant fourth stage. Pegasus is released from its carrier aircraft at approximately 12,000 m (39,000 ft), and its first stage has a wing and a tail to provide lift and attitude control while in the atmosphere. Notably, the first stage does not have a Thrust Vector Control (TVC) system. Pegasus is the world's first privately developed orbital launch vehicle.