PORTSMOUTH - U.S. Sens. Jeanne Shaheen, D-N.H., and Kelly Ayotte, R-N.H., have continued their push to bring the new KC-46A refueling tanker to Pease Air National Guard base by sending a letter of support for Pease to the new Air Force chief of staff.

In Tuesday's letter to Gen. Mark Welsh, Shaheen and Ayotte highlight Pease's unique advantages as a base for the new KC-46 tanker. The next-generation tanker will replace the KC-135 Stratotanker that the Air National Guard flies out of Pease.

According to Boeing, the company contracted to deliver 179 KC-46 aircraft to the U.S. Air Force, the new tanker will revolutionize the Air Force's air mobility mission. The KC-46 is capable of delivering more fuel, three times more cargo pallets and up to twice as many passengers than the KC-135.

The KC-46 is based on the commercial Boeing 767 airliner, which Boeing states is the most fuel-efficient commercial airplane in its wide-body class. Its efficient design will lead to cost savings for the Air Force, with Boeing estimating savings of hundreds of millions of dollars through lower maintenance, depot and repair costs.

Boeing's contract calls for the replacement of 179 of the Air Force's 416 KC-135 tankers. Officials have said that, if Pease does not receive the new tanker in the first go-around, it could still receive the tanker later on. However, the belief is that the longer Pease goes without receiving the KC-46, the more vulnerable it will be to closure during any future rounds of the base realignment and closure process.

Shaheen and Ayotte acknowledged in their letter that it will be a competitive process to obtain KC-46s for Pease, but noted Pease is the "optimal location" for the new aircraft, in light of the metrics the Air Force has selected.

The senators wrote that the basing criteria places a premium on a base's location relative to operational and training refueling tracks, aircraft-related infrastructure and the presence of a flight simulator, and Total Force Enterprise, a combination of reserve and active duty assets and manpower.

"In each of these areas, Pease represents a clearly superior base for the KC-46A," the senators wrote.

The Air Force is expected to release its KC-46 base candidate list before the end of the year. It is not expected to begin buying the new aircraft until 2017. If selected, Pease would not receive KC-46 aircraft any earlier than 2018.