Mitsubishi leaders were ready to face a tough Farnborough air show this month. After all, the company had to delay its Mitsubishi Regional Jet (MRJ) program by more than a year. But they emerged much reaffirmed, thanks to a huge new order from a key player in the biggest regional jet market—the U.S.

U.S. regional carrier SkyWest signed a preliminary agreement for 100 MRJs to be delivered from 2017. The decision is not only a major blow for both Embraer and Bombardier because of the size of the order and the lost business. It also greatly solidifies Mitsubishi's standing as an RJ manufacturer and signals that the long-anticipated change in the established market structure is becoming a reality.

In the narrowbody field, Airbus and Boeing are growing accustomed to the idea that they will have more competitors in the medium term: China's Comac and Russia's United Aircraft Corp. are both developing narrowbodies—the C919 and MS-21, respectively. The incumbents are already competing with Bombardier and its CSeries. Some of these contests have been lost, as in the case of Air Baltic ordering CS300s instead of Airbus A319s.

But it is not only there that the duopoly is a concept of the past. Bombardier and Embraer are now also in the uncomfortable position of having to compete in a much less stable environment when it comes to selling their large RJs. For example, Mitsubishi's market entry is injecting enormous price pressure into the important U.S. RJ replacement tenders and, as the SkyWest order shows, there is a real danger that some of them will be lost.

And if the Canadian and Brazilian airframers ever hoped the MRJ was going to be a niche product for niche players such as Trans States Holdings, then they are now proven wrong. The previous market structure has disappeared. And it is almost unnecessary to say that Trans States confirmed that it will stick to its order in spite of the delay.

The MRJ is the second new entrant in the large RJ segment following the Sukhoi Superjet 100, which entered revenue service last year with Armavia and is now also flying with Aeroflot. But the Superjet has yet to gain full credibility with Western operators in spite of a small follow-on order by Mexico's Interjet, announced at Farnborough.

Clearly, Mitsubishi's clout is growing—and that is in spite of the fact that the first MRJ delivery to All Nippon Airways had to be slipped a year to 2015. Mitsubishi Aircraft Corp. President Hideo Egawa cites two reasons for the delay: Mitsubishi Heavy Industries “went against internal procedures” when it produced initial components. “We cannot use the parts that were manufactured against the rules.” Also, the general development work took longer than expected.

Final assembly is now due to start early next year, with first flight in the third quarter and the first delivery in the second half of 2015. The flight-test campaign will involve five aircraft plus two for the static and fatigue tests.

Egawa says Mitsubishi is still studying the stretched 100-seat MRJ100X for which potential customers such as Air Lease Corp. CEO Steven Udvar-Hazy have been asking. But a decision on launching the third variant of the MRJ family will not be made until after the MRJ90 has started flight tests.

SkyWest's 100-aircraft tentative order is for the MRJ90, the larger of the two versions; but the deal also gives the U.S. regional carrier the flexibility to convert all or part of the order to the smaller MRJ70, SkyWest CFO Michael Kraupp tells Aviation Week.

The eventual type, or mix of types, will depend on what happens with scope clauses at the major U.S. carriers that contract SkyWest to feed their networks. Kraupp says he believes SkyWest, the parent of SkyWest Airlines and ExpressJet Airlines, can make that decision as late as one year before the first MRJ is delivered.

Currently, Delta Air Lines and United Airlines—the carriers for which SkyWest operates most of its aircraft—have scope-clause limits that restrict regional feed to 76- and 70-seat aircraft, respectively. Delta recently reached a new agreement with its pilots union that sustains its cap, but United Airlines is pushing for a higher limit in negotiations on a joint contract with pilots for United and the former Continental Airlines.

American Airlines, a potential future SkyWest customer, also is pushing for a higher cap, using the leverage created by its Chapter 11 bankruptcy proceedings, and US Airways already is able to outsource some flying to aircraft with as many as 86 seats.

The MRJ90 and MRJ70 are designed to seat up to 92 and 78 passengers, respectively, in a single class with 29-in. pitch, but can provide fewer seats with larger pitch or in a two-class configuration. The MRJ70 is expected to be delivered around one year after the MRJ90.

“We'll see where scope clauses shake out,” says Kraupp. The tentative MRJ deal, with the first delivery targeted for 2017, constitutes only a part of the fleet replacement planned by SkyWest. Its subsidiaries currently operate 725 aircraft.

The fleet includes roughly 430 Bombardier CRJ200s, 700s and 900s, and about 290 Embraer 120s, ERJ-135s and ERJ-145s . Kraupp says SkyWest is having “ongoing discussions” with aircraft manufacturers about fleet replacement.

Another agreement, or agreements, might not happen for 12-18 months, but could be reached earlier “if other parties can come to the table in a similar fashion [as Mitsubishi] and offer attractive deals,” says Kraupp.

The tentative Mitsubishi deal, as well as an agreement for 200 Pratt & Whitney PW1200G engines to power them, underscores the discounts that SkyWest can negotiate that other regional carriers cannot because their fleets are not large enough to accommodate large orders, Kraupp asserts. “We don't think there are others in the market that can drive volume pricing,” he adds.

Kraupp also indicated some flexibility in the maintenance terms for the MRJ aircraft and engines, which are still being worked out as part of a package deal. Financing also is still being discussed, but some adaptability is available there as well, depending on the length of the contracts that SkyWest's major airline partners want to sign regarding the operation of the aircraft.