US carrier Frontier Airlines is ordering nine Airbus A321s, its first agreement for the largest member of the single-aisle family.
Frontier's decision takes to 89 the number of aircraft on its Airbus order backlog. The other 80 comprise re-engined A320neo jets.
The airframer confirms the order but says no engine selection has been made. A321s are available with CFM International CFM56s or International Aero Engines V2500s.
Frontier chief executive David Siegel says the type is a "natural fit" for the airline. The carrier has not detailed a seating configuration for the aircraft.