Indonesian carrier Lion Air is ordering 234 Airbus twinjets, including 174 from the re-engined A320neo family.
Its firm agreement covers 109 A320neo and 65 A321neo, and will also feature 60 current A320 jets.
They will be delivered over 2014-26. Airbus values the agreement at $24 billion at catalogue prices.
"The fuel-efficient A320 Family will enable Lion Air to achieve the lowest possible operating costs and continue to offer the most competitive fares in the Asian region," says Lion Air chief Rusdi Kirana.
"This landmark order will ensure that the Lion Air group will continue its expansion with one of the most modern and advanced fleets in the world."
Lion Air has been a loyal Boeing customer, and had previously unveiled a deal for over 200 737 Max aircraft, as part of an agreement for up to 380 737s.