US regional operator Trans States Holdings has firmed up its letter of intent for up to 100 Mitsubishi MRJ jets.
The carrier has signed a firm deal for 50 MRJs plus 50 options.
Deliveries are scheduled to begin in 2014.
Trans States has signed a firm agreement with the MRJ's sole engine provider, Pratt & Whitney, for 100 PurePower PW1200G engines to power the aircraft, along with eight spare engines and options on a further 100.
The carrier has also signed a 12-year exclusive engine maintenance deal with P&W.
Trans States signed the original LOI for the aircraft in October 2009.
Trans States is the only carrier outside Japan to have signed a firm order for MRJs. The only other customer, All Nippon Airways, has placed a firm order for 15 of the type plus 10 options.