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A row over who would be first to receive the European planemaker's latest jet, a revamped version of its best-selling A320, nearly scuppered the deal which also included five more Airbus A380 superjumbos, people close to the matter said.

But the negotiations turned into a public drama, with Qatar Airways' chief executive first saying the deal was off, only to return hours later to announce the signing.

"Every deal sometimes gets stuck especially when the lawyers throw the spanner in the wheel. The price was not at all an issue, from the beginning," CEO Akbar Al Baker said.

"Airbus is still learning how to make airplanes. We have canceled the announcement. There is an impasse. If this is resolved, fine ... If not, then bye-bye," he said in what was now a Boeing press conference.

Neither Qatar Airways nor Airbus would say in any detail what nearly caused their $6 billion-plus deal to blow up.

But people familiar with the matter said there had been difficult negotiations over who should get the prestigious delivery of the first A320neo off the assembly line in 2015.

"It was a walkaway moment," a source close to the deal said.