The Learjet 25 is the third step in the evolution of the Learjet series of airplanes. It received its Supplemental Type Certificate (STC) in 1976. It is essentially a Learjet 24 with its cabin stretched 3 feet to provide comfortable seating for six passengers. There are now eight cabin windows. The engines are GE CJ610-8 power plants that produce 2,950 pounds of thrust and are certified to operate up to 51,000 feet. Between 1976 and 1984, when the Learjet 25 went out of production, 186 units were delivered.