The addition of options to the deal underscores SkyWest’s statement this year that that it might want more than 100 MRJs. The problem, however, is that Mitsubishi Aircraft, struggling with development delays, cannot deliver more than the first 100 this decade. If the options are taken up, the aircraft that they cover will be delivered from 2021.

The aircraft in the firm order will be delivered from 2017, as previously stated. The contract takes the MRJ order book to 165 units, almost three years of production at the maximum planned production rate of five units a month—and much longer when the ramp-up after first delivery is taken into account.

Seeking to offset the development delays, Mitsubishi Aircraft is looking for ways to reach full-rate MRJ production faster than its original, unstated schedule, and then to build faster than the planned rate of five a month.

First delivery to initial customer All Nippon Airways is due in late 2015 or early 2016, at least two years later than the target set when the program was launched in 2008. ANA has ordered 15 MRJs, and Trans States Airlines of the U.S. has ordered 50.

SkyWest Inc. owns SkyWest Airlines, based in St. George, Utah, and ExpressJet Airlines, based in Atlanta, Ga. They operate under the brands United Express, Delta Connection, American Eagle and US Airways Express. SkyWest Airlines also operates flights for Alaska Airlines.

Mitsubishi Aircraft is partly owned by Mitsubishi Heavy Industries, the prime contractor for the MRJ fuselage.