Even with the highly publicized battery problems and other frustrating delays on the 787, “if Boeing had taken a far more aggressive tack in launching new programs like the 777X,” he added, “it probably could have kept this market.”

Boeing has said it had simply been trying to get the designs right for the new planes, and its sales force started pitching airlines and jet leasing companies last spring on the 777X, its name for more fuel-efficient versions of its popular 777 jet. The twin-engine planes now carry more than 300 passengers over long distances, making them economical workhorses for many airlines, and the new versions could carry 350 to 400 people.

Boeing’s board has not yet granted formal approval or money to start work on the 777X, while Airbus has already conducted the first test flight of the A350. Analysts now expect the board to approve the 777X this month, and the airline Emirates has said it might follow that approval with an order for 100 to 175 of the planes, worth perhaps $30 billion to $50 billion at list prices.

Support from Emirates and other large carriers will undoubtedly make the 777X a success over all, the analysts said, especially since the global demand for new fuel-saving planes far outstrips the ability of Boeing and Airbus, the main manufacturers of large airliners, to build them.

But Boeing’s strategy calls for it to be dominant in the sales of midsize and larger jetliners because Airbus has pulled ahead in sales of the newest single-aisle planes, with the A320 neo tallying more advance sales than Boeing’s 737 MAX.