MOUNTAIN HOME, Idaho (AP) — Conservationists are concerned a U.S. Air Force proposal to lower the altitude of supersonic flights around an Idaho air base could have negative impacts on wildlife.

Wildlife advocates fear dropping the flight floors could affect animals in the area covered by Mountain Home Air Force Base airspace, The Times-News reports.

Pilots can already fly low and at supersonic speeds in southern Idaho. The Air Force said it also needs to fly lower in portions of Mountain Home airspace in northern Nevada and eastern Oregon.

The Air Force has started work on a low-level and supersonic flight expansion proposal and is in the development phase of the National Environmental Policy Act process. A draft Environmental Impact Statement analyzing potential impacts of low flights and sonic booms is not expected until next winter or spring.

Idaho public meetings in the Boise, Grand View and Mountain Home presented a general expansion plan.

There could be additional changes to Idaho airspace, Air Force officials said.

The 366th Fighter Wing said in an email that current flight level restrictions inhibit aircrew ability to become proficient in low-altitude tactics.

WildLands Defense Public Lands Director Katie Fite said the proposal should be a major cause for concern.

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“This is happening in some of the most important country anywhere for the protection of wildlife,” Fite said.

Sonic booms and low flights could stress sensitive animals such as bighorn sheep and sage grouse, she said.

“We know noise affects wildlife,” Fite said.

The military continues to ask for expansions at Mountain Home, gradually expanding its footprint, Fite said.

Fite wants flight noise reduced rather than increased, while emphasizing that the forthcoming environmental impact statement needs to include wildlife analysis.