US carrier Frontier Airlines' parent Republic Airways Holdings has tentatively signed to take 40 Airbus A319neos and 40 A320neos.
All 80 aircraft would be fitted with the CFM International Leap powerplant.
The company becomes the first to commit publicly to the A319neo, which is seen as a competitor to the Bombardier CSeries.
Republic already has 40 CSeries aircraft on order.
Airbus disclosed the new agreement with Republic at the Paris air show. Frontier Airlines already operates 58 A318s, A319s and A320s.