An illustration of the LGM-35A Sentinel.

An illustration of the LGM-35A Sentinel. U.S. Air Force rendering

Sentinel flight test delayed more than 2 years

The ICBM program is facing a massive cost overrun and program delays.

The U.S. Air Force’s new intercontinental ballistic missile won’t have its first flight test until February 2026, documents show, putting the costly program further behind schedule.

The new date is a significant delay from last year’s budget documents, which put the LGM-35A Sentinel ICBM program’s first flight test at December 2023. 

An Air Force spokesperson confirmed the delay and said it was pushed back because of “increased lead times for guidance computer components.”

The Pentagon is reassessing the entire Sentinel program after the program exceeded cost projections by 37 percent—and now totals almost $132 billion. Because the overruns breached the Nunn-McCurdy Act threshold, Defense Secretary Lloyd Austin will have to certify the program to stop it from being canceled. 

While the flight test is now slated for February 2026, the program’s schedule will be updated again once the Pentagon finishes the Nunn-McCurdy analyses, according to budget justification documents submitted with the 2025 budget rollout on March 11.

In the meantime, ICBM-builder Northrop Grumman, which was awarded the Sentinel contract in 2020, isn’t halting any work during the Nunn-McCurdy process. 

“Keep in mind that it is both the progress of the missile, as well as the flight test infrastructure— both need to be ready in order to do that full-up flight test. And so I know that that's one of the things the government is looking at right now as they're reassessing the program is the readiness across the infrastructure, not just the individual components,” a Northrop official familiar with the Sentinel program told reporters Monday.

Changes to the Air Force’s original requirements were a main driver of the program’s cost growth, the company official said. Cost estimators had an “undoable mission” of trying to predict the costs given all the uncertainties, the official added.

Specifically, requirements changed for the launch facilities, known as the silos, and for underground cabling that connects the launch sites.

“Changed requirements would be things like adding in fiber optic cabling, where you assumed you'd be able to reuse the copper cables, [and] changing size of launch facilities and aspects of launch facilities,” the official said. “I think those are some of the things that government’s talked about that have led to the change from the cost estimate relative to the baseline.”

And if every silo is a little bit bigger than planned or has an extra component, that drives up cost quickly when multiplied by 450—the number of launch facilities required. 

“The vast majority of it is going to be that multiplier effect of any additional costs that were not expected on the launch facilities or the cabling, multiplied by the vast amounts of it that there are, is going to be the primary driver of the increases there,” the official said. 

Digging up and replacing 7,500 miles of copper cables with a new fiber optic system is particularly challenging because some of the cables are buried on land the government doesn’t own, the official said. 

“When they need to access things like the cabling that runs under that farmland, they need to secure the agreements of a lot of different landowners,” the official said.

Asked about Northrop’s assessment that changing Air Force requirements drove the Nunn-McCurdy breach, a service spokesperson said: “In accordance with statute, OSD will determine what factors caused the cost growth that led to a critical breach via the Nunn-McCurdy process, which is currently underway. Early estimates indicate that a large portion of the Sentinel program’s cost growth is in the command and launch segment, which is the most complex segment of the Sentinel program.”

The size of the Sentinel program is like five major defense acquisition programs, or MDAPs, combined, the Northrop official said. The program can be divided into three parts: a brand new missile, refurbished infrastructure, and operational training and support. 

Northrop will build 25 test assets and 634 missiles, which will be deployed operationally and used as future test missiles until 2075. 

The program also includes refurbishing 450 currently operational Minuteman III silos and building new mechanical rooms and other kinds of support equipment in the launch facilities. 

“There is currently no plan to dig new holes. But I would say that given the site conditions of the land, certainly the potential that when they get to investigating more of the silos, they may find that some of them might not be possible,” the Northrop official said.  

Air Force officials have said they will make the necessary trades to fund Sentinel. And while Congress generally agrees that Sentinel is necessary, some lawmakers are frustrated that the service is committing to the program without knowing what programs will need to be cut to make up for the hefty bill.

Some officials have been “bold enough to say you're going to do this regardless, and you'll make tradeoffs. I want to know what your tradeoffs are. Which one of the programs that have been discussed here by the members of this committee, are you not going to do so that you can do the Sentinel?” Rep. John Garamendi, D-Calif, said during a House Armed Services seapower and projection forces subcommittee hearing March 12.

Services officials could not answer Garamendi at the hearing, reiterating that they don’t know the magnitude of the trade until the Nunn McCurdy process is over. 

Northrop has heard some frustration and “finger pointing” over who got what wrong, the company official said, but “looking for that blame I think is hard, because it really was just an immense challenge.” 

“This is one of the highest priorities that the government has, the nuclear deterrence mission and recapitalizing. Should they have done this earlier, and maybe not put all three of the legs of the triad, all recapitalizing at the same time? Probably, but they didn't. So this bill has come due, and I do think they'll have to find a way to pay it,” the official said.