PIERRE, S.D. (AP) — The first military flying operations are set to begin at an enormous bomber training area over the northern Plains approved this spring after years of consideration.

A spokeswoman for the 28th Bomb Wing out of Ellsworth Air Force Base said operations are scheduled to start Friday at the expanded Powder River Training Complex.

The airspace stretches over the Dakotas, Montana and Wyoming and is the largest training airspace over the continental U.S.

The airspace will be used by B-1 bombers at Ellsworth in South Dakota and B-52 bombers at Minot Air Force Base in North Dakota.

U.S. Sen. John Thune says the airspace is essential to national security and will save on will fuel costs.

Critics have said the bombers will disrupt rural communities and businesses and scare livestock.

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