But critics like Richard Aboulafia, an aerospace analyst at the Teal Group, an aviation-consulting firm in Fairfax, Va., say the main problem is more fundamental: Airbus made the wrong prediction about travel preferences.

He said people would rather take direct flights on smaller airplanes than get on big ones — no matter their feats of engineering — that make connections through huge hubs. "It's a commercial disaster," Aboulafia says. "Every conceivably bad idea that anyone's ever had about the aviation industry is embodied in this airplane."

Richard Aboulafia, an analyst with the Teal Group, said airlines might be more proactive about avoiding hot spots, although he noted that there are very few areas where non-government militaries have weapons sophisticated enough to shoot down a plane.

Richard Aboulafia, vice president of analysis at the Teal Group, believes current narrowbody production rates are sustainable today, "but going up further can be a real problem. You can go up to 50 or 60 [aircraft per month], but if the slightest thing happens you are in real trouble." He cautions that "the idea to go up further is a great way to engineer overcapacity."

Both Airbus and Boeing have already decided to move production rates up for the narrowbody models—Airbus is boosting the A320 line to 46 aircraft per month from 42, and Boeing is moving 737 production to 47 per month from 38 and is pondering 52. Airbus is also looking at rates higher than 50 when the transition to the A320neo is completed.

Aboulafia also is concerned that some emerging players such as Lion Air or Norwegian may not fulfill their promises. Both airlines have large orders for new narrowbodies with Airbus and Boeing. From a macroeconomic point of view, this is worrisome, he says.

To an extent, the situation for manufacturers is as good as it is because of low interest rates (which encourage investment) and the high cost of fuel. These factors can change, and if Airbus and Boeing are unlucky, fuel will become cheaper and interest rates will rise in parallel. Therefore: "We are taking it too far," Aboulafia contends.

And as Emirates, the largest of the Gulf airlines, expands its flights to the United States, some aviation analysts say Delta's arguments are gaining traction. "This is a legitimate complaint," said Richard L. Aboulafia, an aviation consultant at the Teal Group in Fairfax, Va.

Mr. Aboulafia, the aviation analyst, said that Emirates and Etihad Airways, both based in the United Arab Emirates, had already expanded more significantly into Europe, causing problems for European airlines on routes to Asia. "I think that, in the minds of Delta executives, they've seen the future, and it looks like Europe," he said.

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Given the various costs in running an airline, he said, it can be hard to quantify that "a slightly lower capital cost on a plane played a key role in driving you out of a market." But, he said, European authorities had "added insult to injury" by focusing more on providing credit guarantees to help Airbus sell its largest plane, the A380, to the Middle Eastern carriers than on protecting their own airlines

Now, Airbus is preparing to introduce upgraded avionics and other systems that would bring its plane’s features closer to those offered in Boeing’s upgraded 737 Max, which is slated to begin commercial flights in 2017, said Richard Aboulafia, an aerospace analyst with Teal Group, a Fairfax, Virginia-based consultant. “This is something they’ve always done,” Aboulafia said in a phone interview. “Boeing tends to launch all of its big changes in one block. Airbus has more of a rolling update approach.”