The southwest corner of North Dakota may soon be booming, but it won't be because of oil drilling.

Last Friday, the United States Air Force finished the environmental impact statement for the proposed expansion of the Powder River Training Complex, which could lead to expanded military training flights over the southwest part of the state.

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If approved, the expanded training area would be the largest Air Force training space in the continental U.S. and would provide increased training opportunities for the service members at the Minot Air Force Base in North Dakota and the Ellsworth Air Force Base in South Dakota.

Currently, the training area can only handle one or two bombers at a time in the airspace that covers 9 million acres. The Air Force's plan would more than double that space to 21.7 million acres of space allowing as many as 20 bombers, fighters and tanker planes to operate at the same time.

In all, the newly proposed training area would span from the Crow Indian Reservation in southeast Montana to the Standing Rock Indian Reservation in south central North Dakota and from Sundance, Wyo., in the south to Amidon in the north.

But while the enhanced military training space would enable the Air Force to conduct more realistic combat scenarios, it would also restrict commercial air traffic through the region during training exercises and expose residents in the area to noise from the military training flights.

"For the past two years, I've been working closely with the Air Force to make sure it develops a plan that protects the needs of our pilots and airports, as well as the needs of our ranchers, tribes and local businesses," said Sen. Heidi Heitkamp, D-N.D.

Heitkamp said the proposed training area was important for the Air Force's preparedness. But she said it was important to recognize the considerations of residents and commercial airports within the training area too.

"We need to also make sure the Air Force keeps its promise to limit the impact of the expansion on our communities, businesses, local airports, pilots, ranchers, and tribes who rely on our land and unobstructed air space to do their jobs," Heitkamp said in a news release.

According to the plan, residents that live inside the designated training area -- including the cities of Mott, Hettinger, Amidon, Bowman and Lemmon, S.D. -- could see up to up to nine low-altitude flights by military aircraft annually.

Supersonic flights -- where planes break the sound barrier, sending off a sonic boom that can be heard for miles -- would be limited to 10 days a year during large-scale exercises involving roughly 20 aircraft.

Capt. Chris Diaz, the public affairs director at Ellsworth Air Force Base in South Dakota, said those supersonic flights would occur no lower than 10,000 feet above ground level for fighter aircraft, and 20,000 feet above sea level for bombers.

During the training flights, civilian air traffic would be restricted in the area, which covers parts of North Dakota, South Dakota, Wyoming and Montana. The Air Force has estimated that 78 civilian flights a day could be impacted when the largest training operations are conducted.

Kelly Braun, the manager of the Theodore Roosevelt Regional Airport in Dickinson, said he received the executive summary of the plan from the Air Force, but he has not had a chance to read over the document. Braun said he didn't believe the expanded training area would impact commercial flights out of Dickinson.

However, he said that United Airlines provides three flights a day from Dickinson to Denver. Those flights travel directly through the proposed training space.

According to Air Force maps, the training area is meant to simulate air space over Afghanistan.

The plan for the training area has been in the works since 2007 when the Air Force began the environmental impact study to determine how the enlarged training zone would affect the region.

The plan now enters a 30-day waiting period. The Air Force can make its final decision after that time. The Federal Aviation Administration will also need to approve the plan.

The Air Force says that the nuisance of sonic booms over homes, ranches and the four Native American reservations located within the zone have been considered.

Heitkamp said the plan can work for everyone.

"By working together with the Air Force and our local towns and businesses, we can strike the right balance between strengthening our national security and heeding the economic, cultural, and safety concerns of our communities," she said in the release.