Proportionally or by raw dollars, the W80-4 life-extension program would get the biggest increase of any active Department of Energy warhead refurbishment in 2020, if the Trump administration’s budget request became law.

The Lawrence Livermore Laboratory-led life-extension program already got an enormous budget increase in 2019 to pace the warhead’s refurb with development of the Long Range Standoff (LRSO) missile that will carry it, and DoE wants an even bigger one this year: an increase of more than 35 percent, or nearly $245 million, to about $900 million.

That is hundreds of millions of dollars more than the $714 million DoE’s National Nuclear Security Administration (NNSA), in the 2019 budget request it released last year, forecast it would seek for the W80-4 life extension in 2020.

NNSA has not yet explained why its 2019 estimate was so far off the mark. In the detailed 2020 budget request it released Monday, the semiautonomous DoE agency said it was upping its ask for W80-4 in light of the Weapon Design and Cost Report the agency completed for the weapon in December.

The Pentagon is procuring LRSO to replace the 80s-vintage, nuclear-tipped Air Launched Cruise Missile. Boeing [BA], under a contract announced this month, will kit out the B52-H bomber to carry LRSO. The 2018 Nuclear Posture Reviews says the United States will for now maintain 46 nuclear-capable B-52H aircraft. The Air Force has said it plans to buy around 1,000 LRSO missiles. The Air Force plans to deploy the missile in the late 2020s.

Meanwhile, the budget for the LRSO itself would rise about seven percent, or almost $50 million, if the Defense Department’s 2020 budget request becomes law. Raytheon [RTN] and Lockheed Martin [LMT] are maturing competing designs for the missile under four-and-a-half-year contracts awarded in 2017 and worth about $900 million each.

The extra money the Pentagon is seeking for LRSO for the fiscal year that begins in 2020 would go right into those contracts, according to the Air Force’s detailed 2020 budget justification.

Also in 2020, the Air Force plans to “[c]ontinue efforts to conduct parallel development, design, and test activities with the DoE to ensure the LRSO adequately integrates the DoE designed warhead into the system.”

The National Defense Authorization Act for 2019 called on the Pentagon to find some way to speed up development of LRSO, though it is up to the Air Force to decide exactly how.