By Jen DiMascio

The Air Force’s tanker competition comes down to the wire as Boeing [BA] and Northrop Grumman [NOC] yesterday submitted their final bids for the service’s top acquisition priority this year.

At stake is a contract worth up to $40 billion for up to 179 aircraft over the next 15 years. The spoils could be even larger in the future, as the Air Force seeks to replace a fleet of more than 500 aging KC-135 Stratotankers.

In submitting its bid, Boeing emphasized its offering–the KC-767’s technological advancements, capabilities and affordability. “We have completed this KC-X process the way we began it–by listening to our Air Force customer,” said Jim Albaugh, president and CEO of Boeing Integrated Defense Systems. “We believe the KC-767 Advanced Tanker will be evaluated as the most capable, technologically advanced and affordable tanker for America.”

Northrop Grumman touted its KC-30 as a plane with the most capabilities and lowest initial risk.

“Our solution, the KC-30 tanker, not only offers greater capabilities and versatility than any tanker available today, it offers the lowest entry risk. It also meets all of the Air Force’s key requirements and is superior in every respect to the KC-135R it replaces,” said Ronald Sugar, Northrop Grumman chairman and CEO.

With years of future business riding on the competition, both companies have waged a flinty marketing campaign for the contract, and yesterday was no exception.

One of the most obvious differences between Boeing’s KC-767 and the Northrop Grumman-European Aeronautics Defence and Space Co.‘s KC-30 is size.

Boeing, which offers the smaller plane, seized on that disparity, calling the competitor’s plane “oversized” in its press release.

Northrop Grumman sent Defense Daily the following statement in response:

“It should be noted that while Boeing continues to attack the size of the KC-30, size is not an evaluation criteria for KC-X. Boeing keeps raising the size issue because the KC-30 is superior in every Air Force capability category.”

On the matter of cost, Boeing said the KC-767 will save the Air Force and taxpayers $14.6 billion on fuel and $4 billion on maintenance.

That’s an assertion Northrop Grumman contends is not accurate.

“The Air Force will need far fewer KC-30s to deliver the same amount of fuel as KC-767 due to the KC-30s significantly greater fuel carrying capacity,” the statement said, striking out also at Boeing’s technical advancements.

“The KC-767 configuration proposed to the Air Force is a new design integrating components never before connected, including a 767-400 nose, 767-300 wing, 767-200 fuselage. Also, Boeing has yet to build their new boom and has not yet passed fuel through their hose and drogue pod. These are the capability and risk issues that will be considered,” Northrop Grumman said.

A Boeing spokesman dismissed Northrop Grumman’s criticism, saying that the company is advancing the fifth generation boom sold to Japan and Italy on the KC-767 but draws on much of the same technology. He touted the company’s longstanding expertise with tankers.

“Fortunately, the Air Force can only decide what is low-risk and what is media spin,” he said.

That decision could come as early as late this month, though industry and congressional sources say the date may be pushed into February or beyond.

The Air Force declined to comment on the contract award schedule, saying that the information is “source selection sensitive.”

Lt. Gen. Donald Hoffman, the service’s military deputy for acquisitions, is on the record as saying, “We’ll take whatever amount of time it takes to get to the right answer.”

EADS North America also announced yesterday that Saudi Arabia plans to buy three EADS A330 Multi-role Tanker/Transports, which are similar to the KC-30. EADS is providing its tanker to Australia, Great Britain and the United Arab Emirates. Boeing has sold its tanker aircraft to Japan and Italy.