US President Donald Trump’s surprise pitch for a twin-engine “F-55” fighter has reignited debate over US airpower priorities, just as China’s stealth fleet surges and the US doubles down on next-gen platforms.

This month, multiple media outlets reported that Trump has proposed a new twin-engine version of the F-35 stealth fighter, dubbed the “F-55,” during a press event in Qatar. Framing it as a “substantial upgrade,” Trump criticized the F-35’s single-engine configuration, citing safety concerns.

“If an engine goes out, it’s nice to have two,” he said, seated beside GE Aerospace Chief Executive Officer (CEO) Larry Culp. Trump’s remarks, unsupported by official US Department of Defense (DOD) documentation, sparked confusion as no such aircraft exists in US Air Force plans.

The F-55 would require a complete redesign of the F-35 airframe, significantly increasing cost, weight and complexity. Trump also referenced a “super upgrade” for the F-22, calling it “the most beautiful fighter jet in the world,” and alleged that China copied its design for the J-20.

While the White House, DOD and Lockheed Martin declined to elaborate, defense analysts noted similarities between Trump’s F-55 proposal and Lockheed CEO Jim Taiclet’s recent comments on a high-performance F-35 variant offering 80% of the Next Generation Air Dominance (NGAD) – designated the F-47 – capabilities at half the cost.

Observers remain uncertain whether the F-55 represents a serious policy direction or another instance of Trump’s off-the-cuff remarks, echoing his 2018 reference to the fictional “F-52” fighter.

Trump’s remarks on the F-55 have sparked concerns regarding its practicality and significance, especially as the US progresses with the F-47 program and China continues to grow its fifth-generation stealth aircraft fleet.

His ideas, though debatable, underscore significant challenges in US airpower planning, where competing priorities like survivability, readiness and alliance integration clash with the rapid modernization of China’s fighter capabilities.

At the tactical level, having twin engines gives redundancy in case of engine failure, enabling a fighter to return with one engine if necessary while generally offering greater thrust. However, modern single-engine jets show a high degree of reliability, making such an upgrade potentially unnecessary.

According to J J Gertler in an article for Breaking Defense, the F-35 airframe has no more room for a second engine, and that while a twin-engine F-35 could retain the original version’s combat system and cockpit, the plane has to be built around the engine, practically making a new design.

In the same article, Stacie Pettyjohn mentions that redesigning the F-35 to accommodate a second engine would throw off its carefully designed stealth shaping. Pettyjohn says that while Trump’s comments may be unfeasible, it is a sign that the US will keep buying and upgrading the F-35.

However, a twin-engine F-35 may address the type’s relatively short range and small weapons payload, with some tradeoffs in stealth capability.

Looking at China’s J-20 as an example, Justin Bronk mentions in an October 2020 report for the Royal United Services Institute (RUSI) that the twin-engine aircraft acts as a long-range interceptor or strike aircraft, trading agility and stealth for increased range and payload.

Ironically, China may already be fielding its twin-engine analog to the F-35. US Air Force Chief of Staff General David Allvin hinted in a November 2024 interview for Air & Space Forces Magazine that China may have copied the F-35 for its J-35 fighter aircraft, citing a need to protect classified information.

However, China’s limitations in jet engine manufacturing may have necessitated a twin-engine design for the J-35, owing to the use of weaker engines.

At the operational level, introducing a new fighter type may exacerbate the US Air Force’s pilot shortage and lengthy training pipelines. In a January 2025 report for the Mitchell Institute for Aerospace Studies, Heather Penney mentions that the US Air Force has suffered a shortage of 2,000 pilots for 20 years, and that it takes five years for new pilots to be considered “experienced” in their operational aircraft.

In contrast, Derek Solen mentions in a November 2024 report for the China Aerospace Studies Institute (CASI) that China is streamlining its training pipeline, with new trainer aircraft and academies shortening the total training time, replacing four years of progression with an accelerated program.

In practical terms, a new F-55 might require minimal changes to US pilot training, considering the proposed type’s commonality with the F-35, but new tactics or multi-engine checks would add complexity.

US Air Force combat aircraft readiness remains a persistent challenge, which may not bode well for introducing yet another new fighter type in service.

According to data provided to Air & Space Forces Magazine in February 2025, the average mission-capable rate for all fleets was 67.15% in fiscal 2024, down from 69.92% in fiscal 2023 and 71.24% in fiscal 2022.

The report shows low US fighter readiness ratings, with the F-15C and D models scoring 52.9% and 63.7%, the eight-strong F-15EX fleet managed 83.13%, the F-22 got 40.19%, and the F-35A having 51.5%, which are not good indicators for introducing a new fighter type.

Introducing the F-55 fighter may reduce readiness as spare parts logistics and crews adapt. While China is opaque about such statistics, its accelerated training suggests that more pilots will be fleet-ready sooner.

At the strategic level, an F-55 would duplicate many of the capabilities planned for the F-47 program, possibly making the former aircraft type redundant.

While specific NGAD capabilities are yet unknown, Allvin mentioned that the type will have “next-generation stealth, sensor fusion, and long-range strike capabilities to counter the most sophisticated adversaries in contested environments” in a March 2025 article for Air & Space Forces Magazine.

Air & Space Forces Magazine mentioned that Allvin said that the F-47 will also have “significantly longer range” than the F-22, and that US Air Force leaders have discussed the possibility of two NGAD variants – one with longer range for the Pacific theater and another with shorter range for the European theater.

Cost may also be a significant concern with the F-55, as the US Air Force already struggles with other programs such as the Sentinel intercontinental ballistic missile (ICBM) and B-21 stealth bomber.

Taking the F-22 as a cost benchmark for the F-47, Air & Space Forces Magazine says each F-22 costs US$350 million for a fleet of 186 aircraft, while US Air Force officials discuss having a fleet of 220-250 F-47s, with similar costs to the F-22.

Whether the F-55 is a bold vision or Trump bluster, it underscores the mounting pressure on US airpower to evolve faster than rivals like China, without tripping over its ambitions.