Saudi Arabian flag-carrier Saudia is ordering a further 30 Airbus A320neo-family jets of which half will be the new long-range A321XLR variant.
The airline disclosed three years ago that it was taking 35 A320neo-family jets, including A321neos.
But Airbus says it is expanding this agreement to a total of 65 firm aircraft, of which 15 are the A321XLR.
Thirty-five further optioned aircraft mean Saudia is committing to as many as 100 A320neo-family jets.
No engine selection for the aircraft has been disclosed, although Saudia is a strong CFM International customer for its Airbus fleet.
The airline operates about 100 Airbus aircraft – a mix of A320s, A321 and A330s – as well as some 70 Boeing 777s, 787s and 747s.
Saudia has been undergoing a transformation programme which includes a fleet modernisation intended to give the airline some 200 aircraft by 2020.