SkyWest Inc. has finalized an order for 100 Mitsubishi Aircraft MRJ regional jets announced in June, adding options for a further 100, and sticking with its original plan to use the firm order for the larger MRJ90 aircraft—at least for now.

The MRJ90 holds 90 seats in a single class, compared with 70 for the MRJ70. That is significant for U.S. regional carriers, such as the SkyWest subsidiaries, which operate the vast majority of their flights for major carriers under their brand names. That is because scope clauses in the major carrier collective bargaining agreements with their pilots limit by aircraft size and number the amount of flying that can be outsourced to regional carriers.

When SkyWest placed its tentative order in June, Kraupp said the carrier would wait to see how scope clauses at its major airline partners and potential future partners take shape before deciding whether to stick with the MRJ90s. If United Airlines pilots approve their tentative contract when the votes are counted on Dec. 15, the new upper limits will have been established for Delta, United and American Airlines at 76 seats. The only major network carrier higher than that is US Airways, at 90, so the picture could change a bit if it merges with American.

Kraupp now says that, either way, the MRJ90 could be a good fit.

“The MRJ90 can be configured to 76 seats to comply with current scope limitations,” Kraupp told Aviation Week on Dec. 13. “Since the aircraft don’t deliver for a few years, we will see where scope clauses migrate to when making final determinations as to which aircraft to take and how many seats.”

Kraupp says SkyWest probably needs to decide by 2015 whether to switch its order to MRJ70 aircraft. As to which airlines SkyWest will be operating the MRJ for, he says only that “we will have an ongoing effort to offer the aircraft to all of the U.S. majors and see what their appetite is.”

As for its order, SkyWest and Mitsubishi say each batch of 100 aircraft is valued at $4.2 billion, presumably referring to catalog prices. Pratt & Whitney PW1200G geared-turbofans will power the MRJ.

In agreeing to unstated rights and obligations, the companies say they will “mutually position themselves for opportunities in the U.S. airline industry.”