Qatar Airways on Wednesday postponed the delivery of Airbus' first A350-900 just days before taking possession of the next-generation plane built to erode Boeing's dominance in the lucrative long-haul market.
"Qatar Airways announces that the Airbus A350 aircraft ceremonial transfer of title has been postponed until further notice," the airline said in a statement on its Facebook page.
"With the imminent launch of the new Airbus A350 programme, both entities are committed to introducing the A350 very soon," added Qatar Airways.
Airbus chief executive Tom Enders said he was "very confident that our delivery to our customer Qatar will happen very soon."
Shares in the aerospace giant were down more than seven percent on the French stock market, pulling down the broader CAC-40 market, which was down 0.5 percent overall.
Both sides had said last week that the A350 would be delivered Saturday at a ceremony in the southwestern French city of Toulouse.
Qatar Airways has ordered 80 of the aircraft, whose delivery had already been pushed back about a year.
The airline planned to use the new plane for its daily Doha-Frankfurt flight from January 15.
The delivery of a new aircraft is always an extremely delicate task for manufacturers as the client's technical teams scrutinise every detail of the cabin, retaining the right to refuse delivery at any moment.
The Gulf carrier is one of Airbus's biggest clients, albeit a very demanding one.
"We want everything to be absolutely perfect," chief executive Akbar al Baker said in June after postponing the delivery of 13 A380 super jumbo planes, eventually received in September.
"There are issues with the interior and exterior of the airplane," he said at the time.
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- 'Route proving' -
Airlines are in a major push to modernise their fleets to reap the fuel savings that the latest generation of engines offer, especially as competition in the sector is fierce and fuel is one of biggest costs.
The A350, whose wings and fuselage are made of carbon fibre, will save up to 25 percent in fuel consumption.
The plane was designed to help the European aerospace giant catch up with its American rival Boeing.
Airbus invested 10-12 billion euros ($12-$14 billion) in its strategy to position the A350 between Boeing's popular 777 and its 787 Dreamliner, hoping to eat away at both planes' markets.
However with 778 orders for the A350 by November, Airbus was still behind Boeing, which reported booking 1,055 orders for its Dreamliner.
Japan Airlines has ordered 31 A350s and the United States' Delta Airlines has ordered 25.
Airbus chief executive Fabius Bregier estimated a potential 2,500 A350s could be sold eventually.
In August, Airbus had announced that the plane had completed its "route proving", around-the-world in 20 days trip aimed at testing the aircraft's readiness for airline operations, during which it flew 180 hours and stopped off at 14 airports.
The plane, with Trent XWB Rolls-Royce engines, can carry 315 passengers over a distance of 14,500 kilometres (9,000 miles), and to date 39 customers worldwide have ordered it.