The U.S. Air Force has started to examine the attributes of a KC-Z tanker, but it appears that the future of a KC-Y “bridge tanker” is in doubt.

The KC-Y commercial derivative tanker could fill the gap between the fielding of the 179th Boeing [BA] KC-46 and the KC-Z. The KC-46 fleet and possible future tankers would replace more than 400 KC-135s and KC-10s in the coming decades.

“Our plan for the tanker fleet is evolving over time, and we’re having to react to what the threat’s doing],” Air Force Secretary Frank Kendall said on May 3 in response to a question on future tankers from Sen. Tammy Duckworth (D-Ill.) during a Senate Armed Services Committee hearing on the Air Force’s fiscal 2023 budget request.

“At one time, we had a plan for a KC-46 to be followed by a KC-Y ‘bridge tanker’ to a future KC-Z, which hadn’t really been defined,” Kendall said. “As we looked at the requirements, it doesn’t look as necessary or as cost effective as it once did to introduce another aircraft as KC-Y. We’re not sure what we’re going to do about that yet. We haven’t finished analyzing the requirements. But if the needle was over here at competition, it’s moved back toward not necessarily having competition, part of the way anyway.”

Lockheed Martin [LMT] has been gearing up for a KC-Y competition and, in January, said that the company plans to build the LMXT refueler, based on the Airbus A330, in Mobile, Ala., and Marietta, Ga., but Kendall’s comments indicate that KC-Y may very well not happen (Defense Daily, Jan. 31).

The KC-Z may have to survive adversary air-to-air and missile threats hundreds of miles away from U.S. forces’ ground targets.

“As far as KC-Z is concerned, what we do for the next generation, I think that’s gonna be threat-driven,” Kendall said on May 3. “What I’m seeing happening with the threats is that they’re trying to find creative ways to reach out further and engage our tankers at ranges at which they once would have been secure, and that’s gonna be a very big problem for us. We have to re-think how we support our forward tactical aircraft, in particular, and what the tanker of the future looks like in a much broader sense. That work is really just getting underway.”

Last week, the Air Force retired the first KC-10A Extender produced for the Air Force. The plane, which was based at Joint Base McGuire-Dix-Lakehurst, N.J., and which entered service in 1981, moved to its new home at the Air Mobility Command Museum at Dover AFB, Del., on Apr. 26.

Tail number 79-0433 was the first of 60 KC-10As built for the Air Force by McDonnell-Douglas, now part of Boeing.