Qatar Airways is the airline behind a USD$4.9 billion order for 20 Boeing 777 long-range planes listed as an unidentified customer on the planemaker's order book, industry sources said on Monday.

Boeing released a statement saying a final deal had been signed worth USD$4.9 billion including 14 of the 777-300ER (Extended Range) model and 6 of the 777-200LR (Longer Range), only to later retract the statement.

The planemaker has the 20 planes already on its order book as an unidentified customer, sources at the Farnborough Airshow said.

A spokesman for Boeing declined to confirm the identity of the customer.

A spokeswoman for Doha-based Qatar insisted the two sides were still in negotiations.

Airbus sales executive John Leahy also said he remained in talks with the airline about selling similar planes.

Qatar announced tentative plans to buy the planes last September.