Elected lawmakers in the US Congress are attempting to steer plans for modernising the US Air Force (USAF) fleet of air tankers.

A requirement included in the 2024 defence spending bill prevents the retirement of any Boeing KC-135 Stratotankers and bars the USAF from making a final decision on replacing the ageing refueller, until the service has submitted a procurement plan for a next-generation stealth tanker.

The legislation also includes language that could set up a competition between airframers Boeing and Airbus, both of whom are vying for the next phase of the KC-135 recapitalisation programme.

The USAF has 377 KC-135s in service, according to Cirium fleet data, with an average age of more than 60 years. Boeing delivered the first 707-derived Stratotanker to the USAF in 1957.

The effort to recapitalise that fleet includes three phases and potentially covers three new aircraft, initially designated KC-X, KC-Y and KC-Z.


Source: US Air Force

The USAF still operates 377 KC-135s, the oldest of which first flew in 1957. Congress put a hold on the air force’s Stratotanker replacement plan, until the service produces an acquisition strategy for a next-generation survivable tanker

Boeing’s KC-46 Pegasus was selected as the KC-X in 2011, with the first delivery coming in 2019. The USAF contracted with Boeing for 179 examples of the type, with Cirium showing 72 aircraft currently in service.

The final phase of the tanker recapitalisation plan – formerly known as KC-Z – is now called the Next Generation Air-refuelling System (NGAS).

The USAF launched that effort in February 2023, describing the concept as a clean-sheet design capable of surviving in a contested environment featuring modern air defences and fighters.

Air Force secretary Frank Kendall specified in January 2023 that the service wanted a platform custom-built for military operations, rather than a commercial-derivative design.

Just a few months later, in May, Kendall announced the USAF was accelerating the NGAS fielding timeline, now targeting the early 2030s for initial operational capability rather than the original 2040 goal.

That shift brought into question the future of KC-Y – the second phase of KC-135 recapitalisation.

Also known as the “bridge tanker”, KC-Y was meant as a stopgap between the end of KC-46 production and the start of NGAS fielding. Lockheed Martin’s LMXT concept – based on the Airbus A330 Multi-Role Tanker Transport (MRTT) – was the front runner.

The USAF plans to purchase 75 aircraft under the KC-Y acquisition.

However, the acceleration of NGAS called into question the need for a bridge tanker.

“We’ve fundamentally changed our tanker acquisition strategy,” Kendall said during congressional hearings in the spring. “We need to move to a next-generation tanking capability that is resilient enough to survive against a pacing challenge.”

Sensing an opportunity, Boeing began suggesting additional KC-46 orders as an alternative to a third tanker design.

“Pivoting from that, to me would not be the best interest of the Department of Defense or Congress,” Boeing Defense, Space & Security (BDS) chief executive Ted Colbert told FlightGlobal in June. “It frankly would be a waste of time and money.”

Dan Gillian, BDS vice-president and general manager mobility, surveillance and bombers, confirmed the airframer could meet demand for additional orders.

“So long as there’s demand we’ll produce those aircraft for KC-46,” Gillian told FlightGlobal.

KC-46A refuelling KC-46A

Source: US Air Force

Boeing appeared all but certain to secure orders for an additional 75 KC-46 tankers after Lockheed Martin withdrew its bid for the KC-Y programme. However, the latest action by Congress could disrupt, or at least slow, that decision

That seemed to be a forgone conclusion, when Lockheed withdrew its LMXT bid in October.

“We are transitioning Lockheed Martin’s LMXT team and resources to new opportunities and priority programmes,” Lockheed said at the time.

Airbus said it remained committed to independently offering the A3MRTT as a viable solution.

“The A330 US-MRTT is a reliable choice for the US Air Force”, it said on 23 October, “one that will deliver affordability, proven performance and unmatched capabilities”.

With the passage of the 2024 National Defense Authorization Act (NDAA) on 14 December, the proverbial tanker waters have once again been muddied.

In a provision titled “Limitation on issuance of acquisition strategy for the KC–135 recapitalization program”, legislators in Washington have barred the USAF from making a KC-Y decision until a procurement plan for NGAS has been formalised and submitted to Congress.

In addition to a “roadmap timeline” for NGAS procurement, the NDAA also requires a business case analysis for KC-135 recapitalisation and validated requirements for competitive contract award – potentially setting up a showdown between the KC-46 and A330 MRTT.

Following passage of the NDAA Airbus reaffirmed its commitment to offering its A330-based tanker as a KC-Y contender.

“Airbus is grateful that Congress continues to prioritise the tanker recapitalisation programme,” the US subsidiary of Airbus’s defence unit told FlightGlobal on 21 December. “We remain committed to providing the US Air Force and our war fighters with the most modern and capable tanker on the market.” 

Despite the spectre of a competition, Boeing, which had appeared likely to secure the KC-Y contract before the latest congressional intervention, remains sanguine about the KC-46’s prospects.

“We are confident that the US Air Force will pursue the appropriate strategy to continue the recapitalisation of the tanker fleet and meet the needs of the war fighter,” the company told FlightGlobal on 19 December.

Elsewhere in the 2024 NDAA, Congress banned the Department of Defense from retiring or preparing to retire any KC-135s, unless individual airframes are assessed as non-airworthy or non-mission capable and “uneconomical to repair”.

Story updated on 21 December to include comments from Airbus