TAM, which firmed up its XWB deal last week, is expected to be the last of the original group of customers that placed orders or commitments for the A350 "Mk1" variant in 2005 to contract for the new model.
The remaining airline customers, Air Europa and Eurofly, are going for an alternative aircraft type, while GE Commercial Aviation Services will not order the A350 until a GE engine is offered on it.
Air Europa was the first customer to announce commitments for the A350, back in December 2004, with its deal for 10 aircraft coming as Airbus launched the first version of the twinjet.
However, Boeing last week identified the Palma de Mallorca-based operator as the customer for eight firm 787-8s previously listed in the airframer's orderbook for 2007.
Earlier in January, Airbus's chief operating officer customers, John Leahy, expressed doubts to Flight International, flightglobal.com's printed edition, that Air Europa would order the XWB. He also said he did not expect Eurofly to convert its firm order for three of the old A350s to the new model. "I think they'll switch the order over to A330s," he said.
GECAS, which placed a commitment for 10 of the GE-powered A350s back in 2005, has declined to switch to the XWB because it is only available with Rolls-Royce Trent engines. The leasing arm of GE Aviation says its general policy when placing speculative orders is to buy only those with GE engines.
Leahy concedes that the GECAS commitment is the only potential XWB order he has lost because of the absence of an engine choice, but he says talks continue with the US engine maker about a possible deal to equip the aircraft with a GE engine.