The first military flying operations took to the air Friday at an enormous bomber training area over the northern Plains that was approved this spring after years of consideration.

The expansion of the Powder River Training Complex over the Dakotas, Montana and Wyoming roughly quadruples the training airspace to span nearly 35,000 square miles, making it the largest over the continental U.S. Flight operations began after the Federal Aviation Administration finished mapping work on the expanded airspace, a spokeswoman for the 28th Bomb Wing at Ellsworth Air Force Base said in an email.

The airspace will be used by B-1 bombers from Ellsworth in South Dakota and B-52 bombers from Minot Air Force Base in North Dakota. The U.S. Air Force says the expansion will significantly boost training opportunities for Ellsworth and Minot aircrews.

"It'll be the first flights in the newly charted airspace, which again, is something that we think has very positive, beneficial national security implications for our ability to train air crews," said South Dakota U.S. Sen. John Thune, who began pushing for the expansion nearly a decade ago. "At the same time, it's saving money."

The expansion is expected to save Ellsworth up to $23 million a year in fuel costs by reducing the number of training flights to other states.

Ellsworth delayed the first flights for a day after the training complex went active to ensure a smooth transition into the new airspace, said 1st Lt. Rachel Allison, 28th Bomb Wing public affairs chief. Thune, a Republican, told The Associated Press that parts of the expanded airspace won't be active until communications equipment has been installed.

Allison said the complex's first flights took off as scheduled on Friday morning. Outside of large-scale exercises, she said, operations in the new airspace will be similar to flights in the former training area.

Any given location across the training area could experience up to nine low-altitude overflights annually. Supersonic flights would be limited to 10 days a year during large-scale exercises involving roughly 20 aircraft.

The Air Force has said as many as 88 civilian flights a day could be delayed when large-scale exercises are conducted but that the number would likely be smaller.

Opponents of the airspace expansion have argued that the bombers would disrupt rural communities and scare livestock as they roar overhead on maneuvers, dropping flares and chaff, or fiber clusters intended to disturb radar waves.

Thune said he will continue working with the Air Force to make sure that concerns are being addressed.