US budget carrier Spirit Airlines is intending to order 100 Airbus A320neo-family jets, for deliveries which will continue through to 2027.
Spirit says the memorandum of understanding covers a "mix" of A320neo and A321neo jets, as well as the A319neo – the smallest member of the re-engined family which has struggled to land orders.
The agreement also features an option to purchase up to 50 more aircraft.
Spirit Airlines chief Ted Christie says the fleet expansion, once finalised, will support the addition of new destinations across its US, Latin American and Caribbean network.
The carrier says it operates 138 A320-family jets.
These include 64 A320s and 13 A320neos, plus 30 A321s and 31 A319s. Another seven A320neos are scheduled for delivery from Airbus's US plant at Mobile by the end of this year.
No engine selection has been disclosed for the upcoming order, although Spirit is a strong International Aero Engines customer and its current A320neo fleet is powered by Pratt & Whitney PW1000Gs.
Spirit had directly ordered 135 aircraft from Airbus by the end of September this year, and still has 42 A320neos from this total awaiting delivery.
The airline has not indicated how much of the new agreement for up to 150 aircraft would be taken through lessors.
Spirit is to reveal a revamped cabin interior in December including new seating which will provide "additional usable legroom".