The plane carried a crew of six and 22 tons of on-board test instruments. Its first flight was expected to last between two and four hours.

There were cheers and applause as the white jet with a blue tail, its engines surprisingly quiet, picked up speed down the runway and lifted smoothly into the blue skies. Fire trucks were stationed alongside the runway as a precaution.

Airbus chief test pilot Jacques Rosay, flight captain Claude Lelaie and four fellow crew members were taking no chances. Airbus had said they would be wearing parachutes during the first flight, in accordance with company policy. A handrail leads from the cockpit to an escape door that can be jettisoned if the pilots lose control of the plane.

The flight capped 11 years of preparation and $13 billion in spending.

Industry analysts are keeping a close watch on Airbus, which hopes to woo customers away from rival Boeing Co. with the A380 but has yet to prove it can turn a profit on its superjumbo investment, a third of which came from European governments.

As Airbus and Boeing spar over what each calls unfair government subsidies for the other, the rival aircraft manufacturers have staked their success on competing visions of the future of commercial air travel.

The A380, with a price of $282 million, represents a huge bet that international airlines will need bigger aircraft to transport passengers between ever-busier hub airports. But some analysts say signs of a boom in the market for smaller wide-body planes, such as Boeing's long-range 787 "Dreamliner," show that Airbus was wrong to focus so much on its superjumbo.

Just this week, Air Canada said it had firm orders for 32 new Boeing jets, including 14 of the 787, with a list value of about $6 billion, and Air India announced plans to order 50 Boeing jets worth $6.8 billion. Air India wants 27 of the 787s, which will carry up to 257 passengers and have a list price of $120 million, boosting total orders and commitments for the plane to 237. The 787, which was launched a year ago, is scheduled to enter service in 2008.

"If the A380 costs Airbus the mid-market then it's the biggest misinvestment in aerospace history since Concorde," said Richard Aboulafia of the U.S. consultancy Teal Group. "The way the market's changing makes this look more like a science fair project every day."

Airbus, a unit of European Aeronautic Defence and Space Co., is also planning to bring its own mid-sized jetliner, the A350, into service in 2010 — two years after the Boeing 787, but the United States government is demanding no European government launch aid be extended for the A350.

So far, Airbus has booked 154 orders for the A380, which it says will carry passengers 5 percent farther than Boeing's longest-range 747 jumbo at a per-passenger cost up to one-fifth below its rival's.

While plane enthusiasts have lined fences in recent days at the airport in the Toulouse suburb of Blagnac, where Airbus is headquartered, the first flight of the A380 came about a month behind schedule.

Aviation experts said risks remain very slim on the maiden test flight since a plane's aerodynamic characteristics are already well known before it takes off, thanks to years of computer modeling and wind-tunnel tests.

Problems are more likely, but still very rare, later in the test-flight program, when the pilots deliberately take the plane to its limits. An Airbus A330 prototype crashed here in July 1994, killing chief test pilot Nick Warner and six others as they conducted a simulated engine failure exercise.

The test-flight program is likely to finish soon before the A380 enters service for Singapore Airlines in mid-2006, Airbus said — about three months behind the previous schedule.