It has been six months since the US Air Force awarded the contract for its next-generation long-range bomber to Northrop Grumman. The exact terms of Northrop's winning bid to build what the Air Force has designated as the B-21 has been kept secret, but it was based on cost estimates that came in substantially below what the Defense Department's analysis had predicted.

That, along with the classified nature of the budget and the way the Air Force is packaging the project, has raised concerns in Congress that Northrop may have underbid the cost of its proposal to get a foot in the door, with hopes of getting more money later once the project is underway. A report released this week by the Congressional Research Service suggests that legislators may want to take a hard look at that possibility.

The Air Force made cost per plane a key factor in the award of the initial development contract, setting a fly-away cost of $550 million per aircraft (for a fleet of 100 bombers) as the benchmark for bids on the Long Range Strike Bomber program. When Northrop's bid was revealed as the winner, it was also revealed that Northrop had said it could deliver the aircraft at $511 million. But it's not clear what that price tag encompasses. Some features of the aircraft—such as sensors, nuclear weapons capability, and uncrewed flight—could be packaged under separate, classified contracts and raise the cost per plane significantly.

The classified nature of the whole program has made Congressional oversight of the LSRB program difficult at best, since there's no way for researchers to look at exactly what the cost estimate takes into account. Most of the B-21 program is classified as a Special Access Program—making it more highly classified than Top Secret, severely limiting which members of Congress can access information about it. But what is available is a matter of concern to CRS military specialists.

"The winning bid for the B-21 came in substantially below DOD’s independent estimates," noted CRS researcher Jeremiah Gertler in his report. "In the past, contractors have been accused of bidding unrealistically low prices in order to win a given contract, then using their incumbency to appeal for higher appropriations… Congress may wish to revisit DOD’s cost estimation to understand why the estimated cost was significantly higher than the actual bid [and]…may wish to use its oversight mechanisms to verify that the contract can be executed at the price bid and/or select a contract type maximizing contractor responsibility to meet the bid price."

The contract awarded by the Air Force to Northrop is a "cost-plus" contract, with incentive payments added to cost for hitting specific performance goals. Senator John McCain (R-Ariz.), chairman of the Senate Committee on Armed Services, has strongly opposed use of that kind of contract. "I will not authorize a program that has a cost-plus contract—and I told them that," he said in March. "If you have a cost-plus contract, tell me one time that there hasn’t been additional costs, then I would reconsider. The mindset in the Pentagon that still somehow these are still acceptable is infuriating."

Given how the F-35 Joint Strike Fighter program has bloated over time, McCain's concerns appear to have merit. While the B-21 program is supposed to be based on mature technologies and is slated for a much faster delivery timetable than the F-35 program (with delivery to the Air Force within 10 years as opposed to the nearly two-decade-long cycle for the F-35), there's plenty of precedent in Northrop Grumman's last effort (the B-2) for runaway costs.