Around 2024, the Department of Energy’s National Nuclear Security Administration (NNSA) expects to take delivery of a pair of new AW139 helicopters, joining the Air Force in swapping a rotary fleet of Bell [TXT] birds for Leonardo aircraft.

The two Leonardo helicopters for the civilian agency’s aerial measuring system (AMS) fleet will carry the same distinctive livery that the current twin-engine Bell 412s aircraft do: Axalta Starlight Silver, Dark Blue and a Wildcat Yellow stripe, according to the agency’s request for proposals. 

“The delivery of the two units is expected to occur no more than two years after the receipt of order,” an NNSA spokesperson wrote in an abbreviated response to detailed questions about the contract award. NNSA would not comment on which manufacturers or how many pitched aircraft to replace its Bell 412 aircraft, citing “procurement sensitive information.”

Each of the NNSA’s new helicopters will be flown about 250 hours per year, the agency said in its solicitation. When the Leonardo craft arrive, it will mark the second time in less than a decade that a nuclear security fleet has traded Bell’s helos for Leonardo’s. 

The Air Force in 2018 decided to buy MH-139 helicopters, the militarized version of the commercial AW139, to replace its fleet of UH-1N Hueys. Those aircraft, from the same family of Bell-built rotorcraft as the NNSA’s 412 helicopters, are tasked with guarding the Minuteman III missile fields. The UH-1N fleet also provides doomsday VIP transport around the Washington, D.C. area for essential government officials in the event of a nuclear attack. 

For the Air Force UH-1N program, Leonardo went up against the Sikorsky [LMT] UH-60M Black Hawk and a somewhat left-field pitch by Sierra Nevada Corp. to modernize old Army UH-60A Black Hawks into UH-60L “Lima” models.

Leonardo builds the MH-139 — nicknamed Grey Wolf by the Air Force — at the same Philadelphia factory where it will build the NNSA helicopters.

NNSA awarded Leonardo Helicopters a $34.5 million contract for two aircraft on Jan. 24. The NNSA fleet routinely flies low-level grid patterns over major public events like presidential inaugurations or major sporting events, sipping the air for any signs of abnormally high radiation, which could indicate the presence of a nuclear device.