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

What's more, some airport officials say they aren't seeing the demand for the A380 that would warrant the upgrades. "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 aviation analyst Mike Boyd.

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 wing-span is 50 feet wider than the 747, broader than what 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. 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 that several more will be able to land the plane on a regular basis by 2011.

Dan Cohen-Nir, an Airbus North America program manager, said the company is initially targeting the world's busiest airports 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.

Honolulu International Airport is one of many in the country that has no plans to make improvements to accommodate the A380. State Department of Transportation officials say no airline has expressed an interest in flying the A380 to Hawai'i.

Decades ago, some airports also had to make changes to handle Boeing's 747 and other jumbo jets, which brought about a revolution in cheaper air travel. Still, some of the nation's largest airports say the A380 is worth the hassle.

The runways at San Francisco International are so close together that the airport will be able to land only one A380 at a time. The airport has spent just less than $1 billion to build a 23-gate terminal with five gates to handle the A380.