Seattle ? It’s one thing to build a really, really big airplane. But, it turns out, it’s quite another to find a place for it to land.

U.S. airports from Seattle to Atlanta say accommodating Airbus SAS’s new superjumbo A380 in anything other than an emergency would require major construction. Runways would need widening and terminals would need upgrades to load and unload the double-decker plane easily.

Even with those improvements, airports might need to curtail other airport traffic to let the big jet lumber through the airfield. And some officials worry the weight of the A380 would collapse tunnels and buckle overpasses.

What’s more, some airport officials say they just aren’t seeing the demand for the A380 that would warrant such cost and inconvenience.

“Let’s do a cost/benefit analysis: Are you really going to spend millions of dollars (when) you might have two of them a day fly in?” said Mike Boyd, aviation analyst.

Stretching about three-quarters of the length of a football field, the A380 isn’t much longer than Boeing Co.’s latest version of the 747, the largest commercial airplane in the skies until the A380 enters service next year.

But the A380’s 261-foot wingspan is 50 feet wider than the 747, broader than many runways and taxiways were built to accommodate. The airplane also weighs in at a maximum of 1.2 million pounds, 30 percent more than the biggest 747.

The Federal Aviation Administration says just four U.S. airports — John F. Kennedy in New York, San Francisco, Los Angeles and Miami — are formally working with regulators on plans to accept the new plane for passengers. Another two — Anchorage and Memphis — are working with the FAA to take the cargo version.

Airbus says it also has talked with many other airports and anticipates several more will be able to land the plane on a regular basis by 2011.

A crowd gathers near a new Airbus A380 superjumbo after an unveiling ceremony Jan. 18 near Toulouse, southwestern France. The A380 double-deck superjumbo is the world's largest passenger plane. A380's 261-foot wingspan is 50 feet wider than the 747 and weighs in at a maximum of 1.2 million pounds, 30 percent more than the biggest 747.

Dan Cohen-Nir, an Airbus North America program manager, said the company was initially targeting the world’s busiest airports, major hubs that are most likely to need a plane designed to carry around 555 passengers on long international routes.

Still, Boyd and other analysts say the scant interest among U.S. airports could be trouble for Toulouse, France-based Airbus, which has 139 firm orders for the A380 so far.

“For the next decade this is a niche aircraft,” said Richard Aboulafia, an analyst with the Teal Group.

Hubs steer clear

Executives at Boeing’s Seattle-based commercial airplanes division, which makes the competing 747, won’t have to worry about the A380 literally darkening their doorstep. To take the A380 for anything other than an emergency, Seattle-Tacoma International Airport would have to spend tens of millions of dollars just on terminal upgrades. The airport also would have to curtail some other airplane traffic while the plane was on its airfield.

Mark Reis, managing director of SeaTac, said the geometry of the airport “just does not lend itself to operation of the aircraft of that size on a regular basis.”

No airline has expressed a desire to fly the A380 to Seattle, Reis said.

Hartsfield-Jackson Atlanta International Airport is in the midst of a $6 billion airport expansion, but the major upgrade doesn’t include plans to accommodate routine A380 flights. The airport is not willing to make the necessary changes without seeing more airline interest in the A380, spokeswoman Felicia Browder said.

“In the foreseeable future, we don’t think it’s worthwhile,” Browder said.

Denver International Airport would only need minor improvements to land the A380 on more than just an emergency basis. But spokesman Chuck Cannon said there were no plans to make even the minor upgrades, because officials have not heard that any airlines are interested in bringing the plane to Denver, a busy domestic hub that doesn’t see many of the long-haul international flights the A380 was designed for.

Decades ago, some airports also had to make changes to accommodate Boeing’s 747 and other jumbo jets, which brought about a revolution in cheaper air travel. Since then, improvements in aircraft technology have created smaller planes that could fly farther.

Airports make room

Still, some of the nation’s largest airports say the A380 is worth the hassle.

The runways at San Francisco International Airport are so close together that the airport only will be able to land one A380 at a time, and traffic restrictions will be required to let the plane maneuver around the airfield. But spokesman Mike McCarron said the airport planned to take up to six A380s a day, perhaps beginning in the fall of 2006. The airport already has spent just under $1 billion to build a new, 23-gate terminal that includes five gates to handle the A380.

“We have a huge Asian market, (and) we see the A380 as a growth area to the Asian market,” McCarron said.

John F. Kennedy International Airport in New York is spending around $120 million for upgrades including widening one runway and reinforcing taxiway bridges that go over major area roadways. But spokesman Tony Ciavolella said any terminal improvements would have to be done by the airlines who lease those properties.

At Chicago’s O’Hare, spokeswoman Annette Martinez said the airport was working on interim changes that would enable it to accommodate the plane by the end of 2007, while hoping for approval of a big expansion that would make it practical to take the A380 in the long term.

And Los Angeles International Airport plans to spend $53 million on airport-wide improvements, including $2.25 million to make sure underground structures don’t buckle under the A380’s weight.

That’s fine for Los Angeles, officials at Las Vegas’s McCarron International Airport say, as long as those A380s don’t plan to make any unscheduled stops in Sin City. Randall Walker, the Las Vegas airport’s aviation director, said he rebuffed an Airbus request to become an emergency alternative airport for A380s destined for Los Angeles.

Walker said it was not even clear that the airport’s underground tunnels could handle the weight of the airplane. A bigger problem is that one runway would have to be shut down for the A380 to land on another, creating big scheduling headaches for regularly scheduled flights.

Airbus’s Cohen-Nir said the company had found plenty of other airports willing to take the airplane as an alternative, and plans more talks with airports that are hesitant.

“I’m confident that we will be able to show that the amount of disruption is rather limited,” Cohen-Nir said.