• Trump wants an F-35 stealth fighter with two engines because he doesn't like single-engine planes.
• He wants to call this new twin-engine F-35 the F-55.
• A former F-35 program manager told BI that this would basically mean building a new aircraft.

Lockheed Martin's F-35 stealth fighter is equipped with the world's most powerful fighter engine. It only has one of them, though, and President Donald Trump wants it to have two.

That's no small change. Redesigning an F-35 for twin engines is essentially building a whole new aircraft, a former US Air Force pilot who was involved with the F-35 program told Business Insider. That could take decades and require huge expenditures from an administration that's set on slashing government spending.

"The airframe is completely designed around a single engine," explained retired US Air Force Lt. Col. Eric Gunzinger, who worked on the advanced F-35 Lightning II Joint Strike Fighter as a program manager for flight simulation test and evaluation.

"To put two engines in it would be a complete redesign of not only the hardware and the airframe, but also the software," he said. The plane would need to be larger and could see decreased range.

Trump pitched an idea on Thursday for a new twin-engine version of the F-35 that he said he would call the F-55.

"The F-35, we're doing an upgrade — a simple upgrade — but we're also doing an F-55. I'm going to call it an F-55," Trump said during a business roundtable in Qatar. He said that the jet would be a "substantial upgrade" with two engines because "I don't like single engines."

"We're going to do an F-55" if the price is right, Trump said. "And that will be two engines and a super upgrade on the F-35."

The F-35 is a fifth-generation stealth aircraft made by US defense giant Lockheed Martin. It was developed and manufactured as part of a multinational program, and since the first jet rolled off the production line, more than 1,100 have been delivered to the US and militaries overseas.

The F-35 stealth fighter is a cornerstone of US airpower, with not just the ability to penetrate contested airspace but also quarterback American combat assets. While some Trump allies have criticized the aircraft over its high costs and questioned its ability to compete with drones, the president appears to be supportive of the program and the plane's prime contractor, as Trump also wants to upgrade the F-22 Raptor.

Both the F-35 and the F-22 are receiving upgrades, the most notable for the former being the Block IV upgrades and Tech Refresh 3 expected to deliver significantly improved capabilities. The president's plans appear to be outside of these ongoing efforts on the fifth-gen fighters.

In the case of the F-55, it almost certainly amounts to building a new fighter rather than modernizing existing F-35s considering the engineering challenges.

Trump's comments came several weeks after Lockheed Martin's CEO James Taiclet said his company would "supercharge" the fighter aircraft and turn it into a "fifth-generation-plus" aircraft with nearly the capabilities of a sixth-generation fighter like the F-47, which will be built by competitor Boeing. The upgraded F-35 could include improved stealth tech and materials, better sensors, and longer-range weapons. The CEO made no mention of a second engine.

A twin-engine F-35? More like a new F-55 fighter

The F-35's powerful single Pratt & Whitney F135 engine sets it apart from other fifth-generation aircraft like the American F-22 Raptor, the Russian Su-57, and the Chinese J-20 and new J-35, which all have twin engines. The J-35 resembles a twin-engine F-35, at least in appearance.

The F-35's lone F135 engine produces a whopping 43,000 pounds of thrust. The F-22's engines are each less powerful, by contrast, but together create 70,000 pounds of thrust.

Gunzinger, a former F-111 Ardvaark pilot who served with the US Air Force for over 20 years, said that the F-35 has only one engine because compromises were made during development to ensure that the plane met the needs of multiple services simultaneously.

The F-35 comes in three variants: the A for conventional take-off and landing, the B for short take-off and vertical landing, and the C for carrier-based operations. These three variants are generally operated by the Air Force, Marine Corps, and Navy, respectively.

The Marine-operated F-35B is especially unique because of the lift fan that allows it to land and take off in a hover. A twin-engine F-35B is unlikely considering the daunting technical hurdles to build it. "Technologically, it's a bridge too far to put two engines in an F-35B," Gunzinger said.

During his remarks Thursday, Trump said he likes having more engines because there's a backup if one goes out. The only other US single-engine fighters are the F-16 Fighting Falcon and the AV-8B Harrier, the STOVL aircraft the F-35B is replacing.

Gunzinger said two engines are, indeed, better than one, pointing to several instances when single-engine aircraft with engine issues wouldn't have been lost had it had a second engine. But the F-35 is a single-engine aircraft through and through. Anything else is a effectively a different plane.

Talking about transforming the F-35 into a twin-engine aircraft is "talking about a completely different aircraft" that's years — if not decades — away, Gunzinger said. Unless there's a secret fighter jet program underway in the desert somewhere or it is based on Lockheed's failed bid to build the Next Generation Air Dominance fighter, this idea could mean starting from scratch to create a design with the right aeronautics, carrying capacity, and small radar cross-section.

Frank Kendall, who was secretary of the Air Force until late January, told Breaking Defense that "a two-engine version of F-35 would be virtually a complete redesign," adding that the idea is "an option that was never presented and that we never considered."

The White House did not provide further details on the F-55, and neither did the Air Force when BI asked. Lockheed Martin would not say whether it has been in discussions with the White House about a twin-engine F-35 or a new F-55. Lockheed said only that it looks forward to working on the administration's "vision for air dominance."

Gunzinger said that building both the F-55 and Boeing's NGAD doesn't make sense. "The Air Force really can't afford another major fighter program," he added. "With the current budget and capabilities, you really have to decide on do you want an F-55, which is a brand new aircraft, or do you want the NGAD," another brand new aircraft. And both planes would likely bring similar capabilities to the fight.

• Far-right activist Laura Loomer criticized Lockheed Martin and its F-35 jet over the weekend.
• She became the latest Trump ally to lash out against the expensive and highly capable jet.
• Elon Musk has also rebuked the fifth-generation fighter aircraft.

Laura Loomer, the far-right activist who has a direct line to President Donald Trump, criticized Lockheed Martin's F-35 program over the weekend, decrying the US defense giant as "woke" and lashing out against the expensive stealth aircraft.

In a lengthy post on X, Loomer suggested Lockheed Martin is delivering F-35 Lightning II Joint Strike Fighters that "are simply not ready for combat."

"The F-35 program, one of the most expensive weapons programs in history, is plagued by delays, defects, & downright incompetence," she wrote Saturday. She said the US Air Force is accepting jets that lack "functional" radar systems, without offering evidence.

She also claimed that Lockheed is "increasingly obsessed with pushing a woke agenda." Like many other US defense contractors, Lockheed scrapped its diversity, equity, and inclusion programs in January after Trump returned to the White House.

The $2 trillion F-35 program is an appealing target for activists and officials seeking to slash government spending, and it has a well-documented list of problems. The Pentagon's top weapons tester said earlier this year that the program had problems delivering functional software and had fallen behind schedule to test upgraded mission systems.

Despite the issues, the F-35 is fast becoming the centerpiece of US air superiority fighters; the Pentagon approved full-rate production a year ago and plans to buy nearly 2,500 of the stealth fighters. The US military and its allies widely consider it one of the world's top fighter aircraft.

Lockheed has described the F-35's AN/APG-81 active electronically scanned array radar as "the most capable in the world." Northrop Grumman, which manufactures the system, called it the "cornerstone" of the jet's advanced sensor suite.

Loomer criticized the F-35 program's software development, saying some systems are behind schedule, and called out its "deteriorating" stealth paneling capabilities. She cited various media reports to support her case.

The F-35 is the world's most expensive weapons program, with an estimated lifetime cost of over $2 trillion. Other Trump allies, like Elon Musk, the head of the Department of Government Efficiency, have attacked the aircraft as essentially obsolete. Loomer's attack was in some ways the most thorough.

"This is government and taxpayer WASTE on an unimaginable scale, & it's coming out of our pockets!" wrote Loomer, whose opinion swayed Trump to fire the NSA director in early April.

"The F-35 is the cornerstone of the battlespace for 20 allied nations, enabling peace through strength in the 21st century," a Lockheed spokesperson told Business Insider. "It is combat proven, offers the most advanced capability and technology, and is the most affordable option to ensure the US and allies remain ahead of emerging threats."

Loomer could not be reached for additional comment.

The F-35 is constantly being upgraded and reworked to improve its capabilities. It is widely recognized as the world's top fifth-generation fighter, and is in service with militaries in Europe, the Middle East, and Asia. Right now, no US adversary has a comparable platform.

Musk, who criticised Lockheed in the fall, responded to Loomer on Saturday and wrote in a brief post on X: "Crewed aircraft will be destroyed instantly by cheap drone swarms."

Musk made similar comments last year about the F-35's survivability and how drones would make a better alternative. However, airpower experts pushed back on this and said the technology isn't quite there yet.

Musk's DOGE was tasked with eliminating government waste, and defense spending is a big target. Loomer singled out the Tesla CEO in her post and suggested that he — and Trump and Defense Secretary Pete Hegseth — investigate the F-35 program.