US regional carrier Mesa Airlines has signed a memorandum of understanding to order up to 100 of Mitsubishi Aircraft's 76-seat SpaceJet M100 regional jet.

The order from Mesa, announced during the Regional Airline Association's annual event in Nashville, marks a major sign of confidence in the SpaceJet M100, a derivative of the aircraft formerly known as the MRJ.

Mitsubishi Aircraft disclosed development of the M100 at the Paris air show in June.

The memorandum of understanding calls for Mesa and Mitsubishi Aircraft to "commence formal negotiations for the purchase" of 100 M100s, says a Mitsubishi Aircraft media release.

The deal "targets" Mesa placing 50 firm orders and taking purchase rights for another 50, with deliveries beginning in 2024. The aircraft are powered by Pratt & Whitney PW1200 geared turbofans.

At the Paris show Mitsubishi rebranded the MRJ as SpaceJet, cancelled the 70-seat MRJ70 and announced development of the M100.

With 76 seats, the M100 fits snugly within the confines of major US airline "scope" clauses.

Those clauses in US airline pilot contracts specify the size and seat count of the regional aircraft feeding major airlines. The previous 70-seat MRJ70 had fewer seats than competing aircraft like the Embraer 175.

Mitsubishi Aircraft continues developing the larger 88-seat M90 alongside the M100. It expects to begin delivering the M90 in 2020. The company also recently acquired Bombardier’s CRJ programme, giving it a robust global aircraft support network.

“Mesa Airlines’ selection of the SpaceJet M100 confirms that our aircraft fulfills current and future needs in this industry, and that airlines are ready to move our discussions forward," says Mitsubishi Aircraft president Hisakazu Mizutani in a media release.

“With its large cabin, comfort, new technology and low operating costs, the Mitsubishi SpaceJet M100 can deliver this premium experience within US scope clause," says Mesa chief executive Jonathan Ornstein.