Richard Aboulafia, an analyst with the Teal Group, agreed that the engines make sense from both a fiscal and operational viewpoint. "You'd cut fuel and maintenance in half just for starters, and you can lift more and do it faster," Aboulafia said. "It's better across the board and cheaper across the board. There are no drawbacks."

Mitsubishi's problem is Embraer's headstart of over 1,000 aircraft orders, along with an established reputation for financing, reliability and after-sales service, said Richard Aboulafia, vice president of analysis at consultancy Teal Group.

After the MRJ came into the picture, Embraer said it would upgrade its E-Jets with the same fuel efficient Pratt & Whitney engines under the name E2. These will be delivered from 2018 only a year after the delayed MRJ.

"The E-Jet E2 will produce economics every bit as competitive as the MRJ, despite the lack of clean-sheet design," said Morris.

Mitsubishi has a better chance of displacing Bombardier, which has bet big on developing its CSeries to break into the market for 150-seat aircraft at the expense of its CRJ regional jets, said Aboulafia.

"The 350 is a very serious threat and it's very well executed on," said Richard Aboulafia, aerospace analyst for the Teal Group, an analyst firm outside Washington, D.C. "Boeing was dragging its heels on the 777X and the 787-10, the A350 is a far bigger success than it would have had Boeing been quicker."

He added that Boeing's strained relations with its two largest unions is a potential liability, as the company develops the design and manufacture of the 777X.

"Bad workforce relations are a risk," he said. "It doesn't guarantee that you're not going to execute as well as Airbus did on the A350, but it adds risk. Airbus has better labor relations."

"The rollout is a positive development, particularly useful for marketing," said Richard Aboulafia, a vice president of Teal Group, a Virginia-based consultant. "The MRJ order book is a good start for a new player." Still, "the MRJ program needs to prove that it can be competitive even up against the market leader."

Mitsubishi Aircraft wants to take half of the global market for regional aircraft over the next 20 years as Bombardier focuses on its new CSeries jets, which will be able to carry as many as 160 passengers. The CSeries program is also delayed.

If there is any culprit, experts say, it's proximity. "Planes don't make people sick; other people do," said Richard Aboulafia, an aviation analyst at the Teal Group Corporation. "Being around other people, whether it's in the context of a jet, an airport, a hotel, that's going to increase your likelihood of picking up something."

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Although people often suspect that the recirculated air they breathe in the cabin spreads germs, Mr. Aboulafia said that's not the case. "It's nothing to do with the aircraft or the way the air is treated."

Air in a plane's cabin is a mixture of compressed air drawn in from outside and filtered, or recirculated, air. "It all goes through HEPA filters, which are really good at getting particles," Mr. Aboulafia said. "The objective is to filter out all particulate matter," he added, since germs can be transmitted by hitching a ride on airborne particles.