Hill Air Force Base officials are struggling to plan for the future as Congress debates military appropriations in the overdue fiscal year 2018 budget.

Though a nearly $700 billion defense authorization bill awaits President Donald Trump’s approval, Department of Defense appropriations remain uncertain until Congress passes a budget bill, which will decide how much money is allocated to defense.

Officials at Utah’s Hill Air Force Base — still feeling the effects of the 2011 debt-ceiling debacle and subsequent sequestration that capped military spending — told reporters in a conference call Wednesday that they’re concerned.

If Congress doesn’t pass an appropriations bill before Dec. 8, nonessential federally funded activities will stop until a budget is approved, per the Antideficiency Act. That could mean furloughs for civilian employees and a disruption in flying operations at the base, such as in 2013.

If a budget passes and adheres to 2011 Budget Control Act spending caps, Hill officials believe they won’t have enough money to operate the base and achieve their mission of combat readiness.

While the bill to authorize defense spending in fiscal year 2018 would approve $695.9 billion for the Department of Defense, caps restrict the budget to $549 billion. (Fiscal year 2018 began in October.) The Air Force requested $132 billion and would receive $15 billion less with budget caps, said Micah Garbarino, spokesman for the 75th Air Base Wing.

Col. Jennifer Hammerstedt, 75th Air Base Wing Commander, said such a loss of funding could mean choosing among updating aging infrastructure, paying personnel to staff the base or cutting back on weapon modernization.

“Where do we want to make up that difference?” she said.

The base’s budget amounts to a small piece of total Department of Defense allocations, which the approved federal budget would determine — not the National Defense Authorization Act. Congress, whose initial deadline to approve the appropriations bill was Oct. 1, passed a resolution to fund the government through Dec. 8 and is working on the budget’s particulars.

If the president doesn’t sign an appropriations bill before then, or approve another continuing resolution, government services not deemed essential would stop until a budget was passed.

It’s unclear what the defense budget will look like or whether it will comply with spending caps. If it does, Hammerstedt said, base officials could deal with that.

Among their biggest problems, she said, is budgeting for the base long term when officials don’t know how much money they’ll have for the fiscal year until months after it begins.

“Unfortunately we’ve operated like this for several years, so we try to learn from what we did last year, but certainly if you know what your annual budget is, you can be much more effective in planning out for the year,” she said.

In the past, Hammerstedt said, the base has delayed repairing runways, hangars, lodgings and streets to make ends meet, but underfunding programs undermines base workers’ ability to achieve their mission of restoring the Air Force’s combat readiness.

To do that, she said, “the budget not only has to be sufficient, i.e. the right number, but also stable and predictable.”

Brig. Gen. Stacey Hawkins, commander of the Ogden Air Logistics Complex, said the uncertainty affects his operations differently than at the base because the depot functions more like a business.

If he doesn’t know the complex’s budget, he says, he can’t hire people to repair and maintain aircrafts and other weapons, and he can’t purchase other materials necessary to sustain them.

When that happens, Hawkins said, preventative maintenance is delayed, making future repairs more costly.

Part of the problem, he said, is that his complex must maintain the new F-35 fighter jets through their development and implementation states, in addition to the older aircrafts those jets are replacing.

That “fixed pie of the budget” under the spending caps isn’t enough to do both jobs.

Dan Grazier, with the Project on Government Oversight, said those costs are part of what makes the F-35 program so expensive — and why it plays a significant role in the military’s budget.

Though funds for procuring the next-generation jets account for about 3 percent of the proposed budget for fiscal year 2018, that number doesn’t consider costs for maintaining them or for maintaining the aircrafts they were scheduled to replace years ago.

Hill Air Force Base doesn’t use its funds to buy F-35s, but it does maintain the aircraft.

The recently passed defense bill, which is awaiting Trump’s signature or veto, would fund 90 more of those aircraft. Grazier said that isn’t smart use of military money.

Cutting back on the number of new F-35s the military is purchasing is one of the “most obvious” ways Grazier sees to reallocate funds under the military spending cap, especially because the aircraft technically is a prototype.

“That’s the right course of action. Stop buying these things now,” he said. “Finish the development process, finish the testing process and then make decisions about further productions.”

Hammerstedt said while the F-35 program may be costly up front, once implemented, maintenance will be less expensive — and the military will have a fleet of new jets needed to fight in future conflicts.