Vietnamese budget operator VietJet Air is signing for 30 Airbus single-aisle aircraft including the re-engined A321neo.
It will take 21 A321neos as part of an agreement which includes nine baseline A321s.
VietJet disclosed the deal during the Dubai air show.
No engine selection or delivery date has been disclosed.
Airbus chief operating officer for customers John Leahy described the carrier as a "rising star" of Asian aviation.
See the latest news,analysis and opinion from the Dubai air show.