Japan's Mitsubishi Aircraft Corp. has unannounced commitments from customers to buy hundreds of its SpaceJet M100 regional jets, but its first focus is on certifying its larger introductory model, the M90, a senior executive said on Tuesday.

The company's biggest shareholder, Mitsubishi Heavy Industries, last week said delivery of the first M90 would be delayed for at least another year until after March 2021, the sixth delay for the program and a setback to Japan's commercial jet ambitions.

Mitsubishi Aircraft Chief Development Officer Alex Bellamy said a test plane that had around 960 changes from the original design was due to fly in the coming weeks to prove its airworthiness to regulators.