U.S.-made F-16 fighter jets for Ukraine have begun arriving at training centers in the United States, Denmark and Romania. Kyiv’s allies hope the modern aircraft can push Russian aircraft farther from the frontlines, target radar transmitters more effectively and hunt down more cruise missiles.

Commander in Chief of the Ukrainian Armed Forces Valery Zaluzhnyi said in November that F-16s will be "less helpful" now than they would have been a year ago because Russia has had time to improve its air defences.

But they will help address a problem that has persisted from the start of the invasion in February 2022: Russia’s more modern combat aircraft have been difficult for Ukraine’s military to counter with its own aging fighters.

Reuters examined technical documents and spoke to eight military experts, including former F-16 trainers and pilots, about the jets’ capabilities, limitations and the impact they could have on the war in Ukraine.

Early in the war, Ukrainian air defences shot down many Russian aircraft during intense raids inside Ukraine. After just a few months, the Russian air force stopped flying into contested airspace and relied on long-range weapons such as cruise missiles and ballistic missiles for strikes. Ukraine then added layers of additional defences with Western-supplied systems, including PATRIOT batteries that proved effective in destroying even air-launched ballistic missiles. It also uses fighter aircraft, mostly MiG-29s, to shoot down cruise missiles and drones.

Air denial

Making airspace too dangerous for the enemy to fly is a key part of modern military operations.

Western military officials and experts say adding F-16s to Ukraine’s fleet will not abruptly change the course of the war. Training pilots and support crews takes time, surface-to-air missiles remain a major threat, and the jets are not designed for Ukraine's damaged and sometimes makeshift runways.

But they are an improvement on the closest equivalent Ukraine has - the Soviet-designed MiG-29 - and, in the long run, will help Kyiv integrate with Western military allies and break away from reliance on ageing hardware built by its enemy.

“It locks Ukraine onto a technological path that NATO is currently on,” said Robert Farley, a professor at the University of Kentucky who specializes in military affairs and airpower. “What Ukraine has now is a dead end; It’s not going anywhere. If you want to have an air force in 10 years, it’s going to have to be F-16s or something similar.”

The impact

The fighters will replace Ukraine’s strained and thinning fleet of MiG-29s, Su-24s and Su-25s, jets that came of age in the depths of the Cold War.

Ukraine has found novel ways to integrate Western weapons onto those aircraft. F-16s will allow Ukraine’s military to squeeze more performance out of such systems, said Brynn Tannehill, a former U.S. Navy pilot who helped train U.S. Air Force F-16 pilots.

One example is the AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM), which Ukraine uses in a ground-launched anti-air role now, and which will soon be provided for air-to-air use. The AMRAAM C and D models heading to Ukraine can attack targets beyond visual range, but more important they are “fire and forget”: if the pilot has to break radar-lock with a target, the missile’s onboard radar will guide it. Even if there are no dogfights over the front lines, Ukrainian pilots can hunt down cruise missiles more effectively.

More than 4,600 F-16s have been manufactured and sold to more than two dozen countries in many different configurations. Lockheed Martin declined to comment on the specific capabilities of the aircraft being sent to Ukraine.

Since it was introduced in the late 1970s, the F-16 has been upgraded to perform many missions. By the Gulf War in 1990, F-16s were flying regular ground-attack missions with missiles, bombs and anti-radar weapons. Although the MiG-29 can do some rudimentary air-to-ground missions, it’s not made for the task, said Peter Layton, a visiting fellow at the Griffith Asia Institute and former Royal Australian Air Force officer.

“They both started out as a lightweight day fighter, but because Western concepts evolved… (the F-16) gradually evolved into a multirole fighter capable of doing more advanced air defence missions as well as ground attack,” Layton said.

The F-16 can carry more weapons than the MiG-29, Su-27 and Su-25, and roughly as much as Ukraine’s tactical bomber, the Su-24. The versions being sent to Ukraine most likely have an upgraded version of the AN/APG-66 radar, said Kelly Grieco, a senior fellow at the Stimson Center. It can keep tabs on targets on the air and ground, with an air-to-air range past 100km.

Russian aircraft can spot Ukraine’s MiG-29s “much further away than the Ukrainians can spot Russian aircraft,” Grieco said. The more powerful F-16 radars will reduce the radar disadvantage but “will not close it,” she said.

F-16s, and Western aircraft in general, tend to be more pilot-friendly, with intuitive controls and displays that allow fliers to keep their heads up, Tannehill added, calling MiG-29 and Su-27 cockpits “hopelessly out of date”.

The challenges

MiG-29s, and many Soviet-era fighter designs, were meant to operate in poor runway conditions, and have shutters that drop down over their air intakes to prevent the engines from sucking in debris when the plane is on the ground. The F-16’s underslung intake does not have such protections, and it is not meant to operate in austere conditions, Grieco said.

“The F-16 is kind of a precious aircraft, it’s fragile,” she said. “It’s an aircraft that needs a long runway, and the runway is really smooth. But they’re in an environment where (Ukrainian pilots) have been doing distributed operations. … This is not an aircraft that can do that.” To compensate, Ukrainian forces must perform careful sweeps of runway surfaces, a challenging proposition in the midst of a war.

Training enough pilots and support crew to operate the new fleet will take many months.

Eight pilots and 65 support personnel are in the first stages of learning how to operate the F-16 in Denmark; others are in Arizona and southeastern Romanian town of Fetesti. Although the exact number of aircraft has not been disclosed, it is expected to be in the dozens, experts said.

For inexperienced pilots, the first step is familiarization with the new aircraft on the ground and in a classroom. Those elements, plus simulator time, will last about three weeks, said Layton, who transitioned from P-3B maritime patrol aircraft to F-111 bombers during his career. The next step is to ease into flying over the next month. After basic daytime flying has met instructors’ expectations, students would move into night-time, bad weather and instrument flying, which “is a lot more technical”.

Air combat would come next, with six to eight weeks of instruction. Air-to-ground training would last another two months, he said. After basic instruction, U.S. and NATO pilots spend months learning how to carry out more specialized missions.

“It’s not enough just to train them to do the basics if you want to get the most out of those aircraft. You’re going to have to train them to do the complex stuff,” Tannehill said, such as coordinating with ground units or flying multi-aircraft missions.

Even for experienced pilots, learning new systems can be tough, Grieco said.

“If you talk to fighter pilots, they talk about muscle memory: ‘I have to be able to do something where I don’t think, where’s the button?’ she said. “These are people who have split seconds to make decisions.”

Language could be an issue for fliers without much English experience. “Several” pilots and dozens of maintenance personnel are getting language instruction before training in the United States, the Pentagon has said.

Spare parts, manuals and supplies for the F-16s should be plentiful, and the jet is still in production, Farley said. Only about 1,600 MiG-29s were ever produced, and the aircraft are on their way out even in Russia, according to a Royal United Service Institute (RUSI) report in 2020.

Well-trained maintenance crews are crucial, as keeping F-16s in the fight will require regular work—perhaps more than usual if they are operating in difficult conditions. Soren Sorenson, a former Danish F-16 pilot, said maintenance needs would mean each aircraft would be flyable 25%-50% of the time. Layton estimated that each jet would require about 20 maintenance hours between flights, and that on a daily basis, about 25 of every 40 would be ready to fly.

The weapons

In 2022, the United States began supplying Ukraine with AGM-88 High-speed Anti-Radiation Missiles (HARM), a weapon designed to home in on and destroy enemy radar systems. Introduced in the 1980s, it was never meant to be used with anything other than Western aircraft. But by attaching a U.S. weapons pylon to a Ukrainian pylon, the missile was made to work.

It made a quick impact, catching Russian radar operators off guard and forcing them, for the first time in the war, to be careful about when and where they operated, Tannehill said. But the HARMs had to be programmed on the ground to fly to certain coordinates. If there was nothing to lock onto when they arrived, the missiles landed harmlessly.

With the F-16, “you can dynamically program them in flight. The HARM, you can use the full potential because you can change the instructions,” she said.

F-16s also allow Ukraine to upgrade its air-to-air capabilities, Layton said. Ukraine’s radar-guided air-to-air missile inventory is centered on the R-27 model - introduced in the early 1980s. It uses “semi-active radar” guidance, in which the launch aircraft’s sensors guide it to the target.

By contrast, the fire-and-forget AMRAAM and its longer range - the U.S. Air Force lists it as “more than 20 miles” and Ukraine air force spokesperson Yuriy Ihnat said it could hit targets 160km away - may mean Russian aircraft can no longer shoot at Ukrainian planes with impunity.

The future

Ihnat said he did not expect the jets to operate in Ukraine until 2024.

“We will not win the war immediately, but the F-16 is capable of changing the course of events,” he said in August.

Russia has warned against delivering F-16s to Ukraine, with its ambassador to Denmark saying in August that doing so would be “an escalation of the conflict”.

The most important effects, Tannehill said, would be evident not in months, but in years.

“The F-16s are probably going to be necessary to continue to have a viable air force going forward,” she said. “It’s preparing for a future with NATO, it’s modernizing… it’s an infusion of fresh airframes. And that’s going to be important.”