The new airport will be able to handle about 120,000 passengers by 2020, more than twice as many as the current airport, perched atop a bluff near the city with a runway that does not meet FAA standards.

Work on the airport was delayed after The Grand Canyon Trust prevailed in a 2001 lawsuit asserting the FAA had failed to fully consider the noise impacts of the airport over nearby Zion National Park.

"It's Christmas in August," Sen. Orrin Hatch said in a statement.

"St. George is booming, and its airport simply can't keep up with the increased demand for much longer."

Sen. Bob Bennett said the current airport doesn't meet the demands of modern aircraft and the replacement airport will "accommodate the future demands of one of the state's fastest growing areas."

City officials are working on a new cost estimate, which should be completed by the end of the week, and a financial plan.

Construction originally was expected to cost $92 million, but after years of wrangling, litigation and delays, the price tag could come in between $120 million and $150 million.

FAA Administrator Marion Blakey is scheduled to be in St. George next month to hand-deliver the first federal grant to fund the airport.

''This has been a long and sometimes difficult process and we are pleased to finally be at a point where this project can now become a reality,'' said St. George Mayor Dan McArthur.

The new airport, located about 5 miles southeast of St. George, will include an approach procedure intended to keep aircraft as high as possible and west of Zion National Park to lessen the noise impact to the park.

On Monday, The Grand Canyon Trust said that it supports the FAA's final decision, but stands by its challenge to the initial study, which it said was done without consultation with Zion National Park. The Trust rejected Hatch's claim that the airport had been delayed by environmental extremists.

''All we did was ask the court to enforce the environmental laws and regulations and instruct the FAA to do the same,'' said Richard Mayol, spokesman for the group. ''It is not 'extremism' to simply ask that laws on the books be enforced.''

The new airport will be able to handle 70-seat regional jets, allowing more flexibility in terms of destinations and shorter travel times, said Larry Bulloch, St. George's director of public works.

''It would also open the door to additional economic development in terms of being able to accommodate businesses that need jet service,'' he said. ''We're anxious to dive in and move ahead now.''

Bulloch said the old airport, at a prime location near downtown St. George, will be turned into residential and commercial developments to help defray the cost of the new airport construction.