The program to replace aging U.S. Air Force UH-1N Hueys could be delayed two years unless Congress extends access to $83.4 million beyond September, according to a Defense Department reprogramming request.

In the request, the Air Force program to replace its Huey fleet is described as “high risk” for delay because funding to award a contract expires when the fiscal year ends Sept. 30. Congress already approved $86.8 million for the program in fiscal 2017, but that amount is good only for two years.

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The original contract award was planned for June, but a pre-award protest by Sikorsky to the Government Accountability Office delayed it until September. That protest was dismissed in May, but the 100-day delay put funding to award a contract at risk, according to the request. Sikorsky is a business unit of Lockheed Martin [LMT].

To “optimize the use of funds that are expiring” in the current fiscal year, the Air Force is asking Congress to move $83.4 million or risk delaying the contract award until fiscal 2020, the request says.

Industry remains hopeful that Air Force officials will complete source selection and award a contract in September. Initial proposals were due in September 2017 with final proposals for the UH-1N replacement were due this week.

The Air Force plans to buy 84 helicopters to replace its aging Huey fleet. The new helicopter will protect intercontinental ballistic missile fields in Montana, North Dakota and Wyoming and provide emergency transport to support continuity-of-government operations in Washington, D.C.

Boeing’s [BA] MH-139 offering is based on Leonardo Helicopters’ AW139. Rick Lemaster, who is leading the company’s effort to capture the work, confirmed a final proposal was submitted June 17.

“Today turned in final proposal revision, which is the last opportunity to put our best value solution in front of the Air Force,” he said. “We are right-sized for the mission and will be able to perform the mission more efficiently.”

Sikorsky is offering the HH-60U, a variant of the UH-60M Black Hawk while Sierra Nevada Corp. proposes to upgrade old Army UH-60A Black Hawks into UH-60L Force Hawks.

“We remain confident the Sikorsky HH-60U offering is the strongest, most capable and only technically compliant solution for the UH-1N Huey replacement program,” Sikorsky said when its pre-award protest was denied in May.