With the expansion of LAX mired in turmoil, another L.A. airport is doubling its capacity with nary a peep from local politicians, homeowners or environmentalists.

Ontario International Airport, which is owned and operated by the L.A. Department of Airports, is completing a major expansion that includes a pair of new 265,000-square-foot passenger terminals, a transportation center, parking lot and roadway system.

When the $250 million project is completed, as expected this September, the airport will be eight times larger than the current facility and able to accommodate 10 million annual passengers. That compares with the 6.5 million who traveled through the airport in 1997.

Ontario officials say the expansion will enable the airport to satisfy increasing demand for air travel in the fast-growing Inland Empire, and position the city as the area’s dominant transit and business hub.

And in stark contrast to the increasingly bitter fight over LAX’s controversial master plan, there appears to be little, if any, organized opposition to those ambitions. Even the local Sierra Club chapter has not raised objections.

“We’re all looking forward to the expansion here,” said Alan Wapner, the city’s mayor pro tem.

Such enthusiasm is welcomed by opponents of the LAX master plan, led by L.A. City Councilwoman Ruth Galanter, who argue that rather than boosting the capacity of Los Angeles International Airport, the city instead should consider a regional approach to meeting air transportation demand.

“They shouldn’t be doing an LAX master plan, they should be doing a Department of Airports master plan,” Galanter said. “Ontario is in one growth area of the Southern California metropolis. It is an appropriate place to look at increasing air service.”

The city of L.A., which purchased the Ontario facility in 1967 as a backup to LAX, also owns airports in Palmdale and Van Nuys.

Opponents of expanding LAX insist that Palmdale, where the city owns some 18,000 acres of land, could be a viable alternative particularly if the airport is connected to the rest of L.A. with a high-speed rail link. But Palmdale recently lost its sole commercial carrier when Shuttle By United canceled its commuter flights to LAX.

Elsewhere in the region, Burbank, John Wayne and Long Beach airports already offer commercial airline service, although the three operate under varying capacity constraints and their future growth is in question.

In addition, airfields exist at several former Air Force bases El Toro in Orange County, March in Riverside and Norton in San Bernardino that planners say could be developed into commercial operations. And a small municipal airport in Oxnard, which sends eight commuter flights a day to LAX, is another airport that could potentially pick up additional capacity.

Backers of the LAX plan argue that while expanding capacity throughout the region is a fine idea, none of the existing airfields would be able to accommodate an expected explosion of passenger and air cargo demand over the next two decades. Under the proposed $8 billion to $12 billion expansion plan for LAX, the airport would grow from 60 million passengers a year to 100 million. It also would add about 4 million square feet of cargo space.

Ontario officials admit that their airport will never replace the mighty LAX. But they intend to grab as large a piece of the air transit pie as they can.

“We’re ready and willing to do our share, to share the regional load of traffic,” said airport spokesman Dennis Watson. “We’re poised in a very good position now.”

Ontario’s current single terminal, built more than 30 years ago, was designed to handle about 3 million passengers, although more than twice that number passed through the airport last year.

About 250 flights a day take off or land about 40 of them cargo flights and most of those for UPS, which has been operating a major distribution facility in Ontario since 1981. A few years ago one airline offered service from Ontario to Mexico hence the “international” designation but those flights have been discontinued. However, the potential is there: The airport has two 12,000-foot runways, capable of accommodating aircraft of any size.

City officials claim that the airport contributes more than 55,000 jobs and $5.4 billion each year to the regional economy.

And unlike other regional airports in Orange County or Long Beach, Ontario has room to grow.

A proposed third terminal would increase passenger capacity to about 15 million a year. The airport also intends to increase cargo operations by redeveloping a 70-acre location vacated by Lockheed and a vacant Air National Guard hangar. The Department of Airports also has purchased about 170 acres of land adjacent to the airport for future expansion.

That may be necessary. A recent study by the Southern California Association of Governments identified the Inland Empire as one of the fastest-growing regions in Southern California, projecting that the population of San Bernardino and Riverside counties will almost double to 5.6 million by 2020.

In the meantime, the airport plays a central role in Ontario’s economic development plans, which consist of marketing the city as a Southern California destination in its own right.

Already, 17 million people visited the massive Ontario Mills outlet mall and entertainment complex last year. Ontario also has a new convention center, several new hotels, the California Speedway and plans to construct a sports arena to attract minor league basketball and hockey to the area. The city’s proximity to attractions like Disneyland, the San Bernardino Mountains and Joshua Tree National Park also could make it attractive to tourists.

And if the airport gets overflow air traffic from people put off by traffic and congestion in Los Angeles, so much the better, said Wapner, the city’s former mayor.

“We’re an alternative for folks in the basin,” he said. “Whether or not LAX is able to expand, Ontario has some expanding potential and we’re happy to try and meet that.”