First manufactured in 1977, the Learjet 28 Longhorn became the first production jet to use winglets in its design. This wing design increased operating efficiency by lowering induced drag around the wingtips, and the aircraft sought greater fuel efficiency at a time when fuel prices were skyrocketing. The Learjet 28 was powered by two General Electric CJ-610-8A turbojet engines that produced 2,950 pounds of thrust, but these engines were outdated for the time and made the aircraft an unpopular choice. Only five Learjet 28 aircraft were built.