FARNBOROUGH, England — The Pentagon is seeking "consideration" from Boeing as a result of the KC-46A Pegasus tanker missing a major program benchmark, even as the company begins flight tests on its redesigned refueling system.

In May, the Air Force announced Boeing would miss a deadline to have 18 tankers ready to go by August of 2017. Instead, those 18 aircraft will be ready come January 2018, barring any further delays. Because the development contract for the tanker caps the Air Force's liability at $4.9 billion, with the company having to absorb the rest, there have been no cost overruns for the service directly; the company has already been hit with $1.5 billion in cost overruns.

However, there are potential costs for the Air Force due to delays in the KC-46. Specifically, the service may have to fly the KC-135 fleet for longer. That raises the question of whether Boeing would be asked to help cover some of those down-the-line costs for the service.

Frank Kendall, the Pentagon's top weapons buyer, said the tanker program office is currently running an analysis of the costs for the service that can occur due to the delay.

"There is no penalty specialized in the contract for a schedule slip," Kendall said. "Any delay just increases that number. I think Boeing is highly motivated to get this done.

"That said, the government is losing some of the value that we have contracted for, so we are entitled to some consideration for that. The program office has several ideas for how we might do that, and they're talking to Boeing."

For its part, Boeing is focusing less on potential punitive measures and more on the technical aspects of fixing the KC-46 boom, which has been the source of the recent delay.

Boeing defense head Leann Caret told reporters Sunday that the company began flying the redesigned boom in the last week. The design features a bypass, roughly the size of a paperback book, which helps control the fuel flow while refueling heavier aircraft such as the C-17.

Caret reported "positive" results from early tests, and Kendall said he was "cautiously optimistic" that the bypass would fix the boom issues for the tanker.

"It has some indications very recently over the past weekend that they're having some initial success from the hardware and software fix, but it's too early to have a definitive answer to that," Kendall said.

Twitter: @AaronMehta