Production of the Airbus A340 four-engine commercial jetliner has ended, making it Airbus’ shortest-lived production model. The aircraft entered service in 1993, but soon began losing favor with carriers due to the economic factors associated with feeding fuel to and maintaining four engines. Demand for the A340 also took a major hit with the expansion of extended operations or ETOPS. As regulators increased the amount of time twin-engine aircraft were allowed to fly away from suitable landing sites under more lenient ETOPS regulations, four-engine aircraft lost a key competitive edge. And, Thursday, Airbus confirmed that it had sold zero A340s over the past two years. Meanwhile, some twin-engine jets from competing manufactures have done quite well.