AMARILLO, Texas -- Deep beneath the dry, dusty ground outside this Panhandle city lies something lighter than air: helium.

But the supply of the gas that inflates balloons, cools MRI machines and detects leaks in NASA space shuttle fuel tanks isn't infinite.

There's only so much helium in the world, and some fear that a shortage is coming.

"Once it's used up, it's gone," said Rasika Dias, professor and chairman of the chemistry and biochemistry department at the University of Texas at Arlington. "What we have is what we have."

Still, nearly two dozen underground wells about 15 miles northwest of Amarillo work round the clock to retrieve helium and pump it to customers connected to a nearly 450-mile pipeline that stretches from the Panhandle through Oklahoma and to Kansas.

This site -- thousands of acres where cows and antelope roam -- is home to underground gas fields and the country's only Federal Helium Reserve.

More than one-third of the world's helium supply comes from this site, including nearly half of the U.S. supply.

But even helium officials in Amarillo say that after more than a half-century of steadily providing the world with helium, the facility's production days are numbered.

"There is just a finite amount of helium out here," said Leslie Theiss, field office manager for the Bureau of Land Management's Amarillo field office. "There's only so much we can do.

"The clock is winding down on this place."

That seems to be what the government wanted more than a decade ago, when Congress passed the Helium Privatization Act of 1996, calling on reserve officials to sell off most of their helium by 2015. The latest projections show that all the helium won't be sold on time, but it could be gone by 2020.

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