On a brisk Tuesday in January, two military planes flew over the Desert National Wildlife Refuge about 70 miles outside of Las Vegas. From the sand dunes underneath regulated airspace, the meandering planes blasted flares into the empty blue sky and then gradually, they left the area.

They might have been U.S. military planes, an officer said that night at an Air Force open house in the Aliante Hotel and Casino. Another possibility, he said, was that they belonged to the British Royal Air Force, which had units in Southern Nevada for an annual military exercise.

When the planes were gone, the largest wildlife refuge in the lower 48 states was close to silent, one of the few places where there is very little traffic, by foot or by vehicle — the road into the refuge was unpaved and rocky at parts. From the driver’s seat of a gray Toyota Tacoma, Patrick Donnelly, Nevada state director at the Center for Biological Diversity, said that was what made the refuge unique. It had so far lived up to its mission statement: to protect the bighorn sheep.

“Bighorn [sheep] need vast undisturbed areas of wild country,” Donnelly said.

Much of the land West of the refuge belongs to the military. Between Nellis Air Force Base, the Nevada Test and Training Range and Creech Air Force Base, it manages millions of acres in Southern Nevada. Under a new proposal, that footprint could expand. Military officials argue that an expansion is necessary to replicate the realities of modern-day warfare.

Donnelly is working to block that from happening, and he is not alone. More than 200 people showed up to a public hearing on the plan at Aliante Jan. 23. Dozens spoke out against the project and nearly all of the comments were in opposition to it. At the hearing later in the day, activists carried signs that said #Don’tBombtheBighorn.

That line of argument might be a stretch. The military does bombing exercises on the Nevada range but the Air Force is not proposing to extend bombing into the thousands of desert refuge acres proposed for withdrawal. The Air Force Warfare Center, which is overseeing the process, said the military needs more space to conduct irregular warfare exercises safely and efficiently.

“This range is a 1990s range,” said Jim Sample, a civilian Air Force staff. “When we [tested] our older weapons systems, our ranges were short. We dropped our weapons close to the target."

Fifth-generation jet fighters like the F-35 and the F-22, which drop weapons from farther away, mean that the training ranges like the Southern Nevada test range need to expand, Sample argued: “The proposal allows us to operate more like we do in real combat, where we have the airplane fly in higher and drop the weapon sooner before he gets near the bad guys.”

But in context, the military’s ask is a big one.

The test range already spans 2.9 million acres. Under this proposal, the Air Force would ask Congress to transfer an additional 300,000 acres from the refuge and other federal land. The military could also get primary jurisdiction to conduct more exercises within 850,000 acres inside the refuge that the Air Force currently manages with the U.S. Fish and Wildlife Service.

So from Donnelly’s perspective, it’s a 1.1 million acre withdrawal, and as he drove along the refuge’s bumpy access road, he argued enough is enough. “They are talking about dozens of miles of roads,” he said, which could disrupt habitat for Bighorn sheep and desert tortoises.

The message to the Air Force Tuesday night was the same: Work within the boundaries you have. “There are other ways they can operate,” one speaker told the packed Aliante conference room.

The debate strikes at a broader issue of how public lands should be controlled in Nevada, a state where the federal government manages about 80 percent of land. Local communities are often frustrated by the federal government’s role, which can restrain ranching, conservation or development. And several commenters said the areas that the Air Force already occupies, in addition to those it wants to annex, have historical significance for rural and tribal communities.

Varlin Higbee, a Lincoln County commissioner, recalled how, as a small boy, he would climb up on his family’s windmill and watch about 200 sheep come to water. The Air Force now controls that land.

“The grazing that goes along with the ranching has been diminished a good 20 to 30 percent,” Higbee said during his public comment. “Our economy is a struggling economy.”

Although the expansion would largely affect traffic in the sky, the Air Force expects there would be some construction on the ground. Under one plan, the military would build fencing around the range and construct about a dozen concrete pads on the roads to simulate enemy radars. The Air Force might also decide to land aircraft on a dry lake bed.

“We are talking about disturbing maybe 24 acres,” Sample said.

President Franklin Roosevelt established the Desert National Wildlife Refuge in 1936 through an executive order aimed at protecting bighorn sheep. But much of the western part of the refuge was closed to the public as World War II and the Air Force started conducting nearby bombing practices.

Aerial photos show that much of the northern part of the training range has been pockmarked by munitions over the years. But the southern range, where the Air Force is vying for more control, remains largely untouched. Bombing occurs in a small part of the southern part of the range, and the military is required to treat much of the range like wilderness. Even though the Air Force has said it wouldn't extend its bombing footprint, some groups remain wary. They worry that the expansion could limit their access.

Donnelly parked his car in a desolate turnoff inside the refuge about 30 minutes from highway 93. He pointed out a series of well-preserved petroglyphs, depictions of bighorn sheep from thousands of years ago. There was a pile of flakes on the ground. Donnelly said the rocks were likely shavings from Paiute tools. The Moapa Band of Paiutes considers the land sacred.

Greg Anderson, chairman of the Moapa Band of Paiutes, said that he opposes expansion onto land that is important to his community, especially one that might threaten a species that the Paiute tribe views as protectors. Mountain sheep songs are among the tribe’s most important.

“They don’t know our culture,” Anderson said.

If the Air Force gets its expansion, Anderson said the federal government should expand the tribe’s lands for economic development, mainly the construction of large-scale solar projects.

The Aliante meeting was one of five public hearings the Air Force held in January. The public has until March to file a comment on the draft environmental assessment. Comments can be submitted online or by mail.

Congress must decide what to do about the issue before 2021, when the law permitting the testing range expires. Most observers expect Congress to act on an accelerated timeline.

It’s unclear what action Congress plans to take in the near-term. Several groups have been to Washington, D.C. in recent weeks to lobby the delegation. Some conservationists worry Congress could bypass the final steps of the environmental analysis by folding the withdrawal expansion into the National Defense Authorization Act, which often has hundreds of amendments.

Jose Witt, the Southern Nevada director for the Friends of Nevada Wilderness, said Congress should wait until 2019, when the environmental assessment is scheduled to be completed.

But he acknowledged, “Congress can do this whenever they want.”