Jens Flottau Farnborough and Andrew Compart Washington

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.