FARNBOROUGH, England — The U.S. Air Force’s contract for a replacement to the UH-1N Huey helicopter could be delayed until fiscal 2020 unless Congress adds another $83.4 million to the program.

According to a reprogramming request sent by the Defense Department to Congress, the UH-1N replacement effort is currently considered a “high risk” program due to a pre-award protest by competitor Sikorsky, a Lockheed Martin subsidiary, which was dismissed in May.

The protest had temporarily put a hold source selection, deferring a contract planned for June to September. Current funds would expire at the end of the fiscal year on Sept. 30, meaning that if an award was further delayed it would take until FY20 to inject more money to continue on with the program, the request stated.

Air Force Secretary Heather Wilson acknowledged in May that the contract could be awarded sometime this fall.

“We’re going to try and not let that slip too much because we know we need to get the Hueys replaced, but we did get a delay,” she had said.

The Air Force’s aging UH-1Ns are most well-known for the role they play defending nuclear missile sites, and it is the importance of this mission that has led to criticism from leaders in Congress and in the U.S. military — including U.S. Strategic Command head Gen. John Hyten — who have said the service needs to move more quickly to procure new helicopters.

Three companies are competing for the Huey replacement award, with the first of a total of 84 new armored helicopters expected for delivery as early as 2020 — although if a contract is delayed until FY20 it seems likely that fielding will not be possible for another couple of years.

Sikorsky is offering the HH-60U, a version of its UH-60 Black Hawk helicopter with modifications like a rescue hoist and electro-optical sensor. Sierra Nevada Corp. has pitched a modernized, life-extended version of used Army UH-60L aircraft that its calling “Sierra Force.”

Meanwhile, Boeing and Leonardo are partnering on the MH-139, a militarized version of the Italian firm’s civilian AW139 helicopter. Boeing submitted the final proposal for the aircraft Tuesday, it confirmed in a statement.

“The Boeing MH-139 is capable, affordable, and ready to serve the United States Air Force’s urgent UH-1N replacement needs,” the company said. "With a hot production line in Philadelphia, we are well-positioned to meet the USAF’s delivery requirements for fielding this vital platform as soon as possible.”

While the requirements for the helicopter were not made public, the Air Force has specified nine fully loaded troops without needing to be refueled for an endurance of at least 225 nautical miles. They also should be able to fly three hours while maintaining a 135-knot cruise speed.