Airbus SAS said yesterday that it will delay delivery of the world's largest commercial jet by six months to the latter half of 2006.

The Toulouse, France-based company cited several factors for the delay of the A380 aircraft, including difficulty in meeting air carriers' specific configuration requests and problems getting the plane's parts from suppliers in time. The company also said that it is unable to assemble the planes as quickly as it had anticipated. Mary Anne Greczyn, spokeswoman for Airbus North America Holdings Inc., said delays in delivering new aircraft are not uncommon.

"This is a new aircraft program, the magnitude of which has never been seen before," Greczyn said. "Even at this level of evolution of an aircraft, there are always delays when the first one comes out."

Australian carrier Qantas said yesterday that Airbus had notified it of the delay, and the carrier said it would seek compensation. Air France said it also was notified about a two- to six-month delay for its 10 A380s. Lufthansa said it has not heard from Airbus about its airplanes scheduled for delivery at the end of 2007.

"We are developing contingency plans to ensure there is no impact on our schedules or available capacity during the six month delay," said Qantas Airways Ltd. chief executive Geoff Dixon in a statement released yesterday. "We will be working closely with Airbus to ensure the new deadline is met."

The delay comes as Airbus and its U.S. rival Boeing Co. are engaged in a fierce competition for leadership of global aircraft manufacturing. Both companies are launching new aircraft and touting their visions of the future of passenger air travel.

Airbus edged past Chicago-based Boeing to become the world's largest aircraft manufacturer in 2003. Its A380, which can carry at least 555 passengers, is aimed at easing air-traffic congestion at global hubs by fitting more people into bigger planes. The Airbus vision foresees an increase in new passengers from Asia and the Middle East flying to destinations around the globe. Boeing, meanwhile, is building a smaller, more fuel-efficient plane with new technology to provide passengers with point-to-point air service to new markets.

The aircraft rivals also have become embroiled again in tensions over government subsidies. U.S. Trade Representative Rob Portman this week said he would move ahead with a U.S. complaint to the World Trade Organization over European government subsidies to Airbus to launch new airplanes. European officials said they would likewise go before the WTO to complain that Boeing has received local tax breaks and military contracts that amount to subsidies.

After falling behind Airbus, Boeing appears to be picking up momentum this year. The company has racked up 266 orders from 21 customers for its new aircraft, the 787 Dreamliner, scheduled for delivery in 2008. Airbus has struggled to launch a 787 competitor called the A350. An Airbus executive said the company will announce 100 orders for the A350 next week at an air show in Paris.

Boeing declined to comment yesterday on the A380 delays.

Airbus launched the A380 to take on Boeing's signature 747. The A380 can be configured to carry about 1,000 passengers on two full decks and includes features found on an ocean liner, including a wide staircase connecting the two levels. Airbus has 154 orders for the plane, which carries a list price of $280 million. No U.S. passenger carrier has ordered the aircraft, but many airlines such as Singapore Airlines, Emirates, Air France and Qantas have ordered the plane in hopes of squeezing more passengers into major airports that have limited capacity.

One aerospace analyst said the delay, which Airbus said was revealed to the aviation press in April, was not unusual. But, he added, it raises questions about whether the plane is meeting performance specifications, such as in fuel efficiency, that have been promised to customers. "Delays, in and of themselves, are not a big deal," said Richard Aboulafia, an analyst at Teal Group. "But if it means anything in terms of the economic promise of the plane, that is more serious."

Another analyst, Paul Nisbet, of JSA Research, said the six-month delay is "fairly unusual" and could cause uncertainty for Airbus customers. "How long is it going to be before they get back on schedule? Are they going to have to delay all deliveries for the next year or two or three?"

The Airbus A380 made its maiden flight last month. The French company now says it can't deliver the largest commercial plane until the latter half of 2006.