The F-16 jets that the Ukrainian military is touting as a potential gamechanger in its conflict with Russia will either be restricted to defense or deployed in very high-risk operations, according to people who’ve flown the planes in combat.

The General Dynamics Corp fighter-bombers will be a significant upgrade on the Soviet-era planes that Ukrainian pilots have been flying so far. But the F-16s that are likely to be sent to Ukraine will still have inferior radar and shorter range missiles that the most modern Russian jets and air defenses.

“It’ll be like they pushed the easy button or switched from driving a Lada to a Honda Accord,” says Brynn Tannehill, a former aviator who designed simulatros for F-16s, referring to the notoriously clunky Soviet-era Lada car. All the same, she added, “you can’t overcome the laws of physics.”

That means that the Ukrainians may have to rein in their stated expectations that the F-16s will enable them to to impose air superiority, shoot down cruise missiles and the latest enemy jets, destroy troops and artillery on the battlefield, and even sink the Black Sea Fleet. The jets would, instead, give Ukraine “an incremental capability that they don’t have right now,” US Air Force Secretary Frank Kendall said at a briefing on Monday.

Were they to fly at Russian lines to take out artillery, air defenses, or jets, Ukraine’s F-16 pilots would likely get an alert to signal detection by enemy radar long before getting close enough to shoot, according to John Venable, a former F-16 pilot in the US Air Force.

“All you can do is dive for the dirt and hope you can put a hill between you and the missile’s guidance systems,” said Venable, now a senior research fellow for defense policy at the Heritage Foundation, a Washington think tank. Without that cover “your chances of survival are not great,” he said.

That’s likely to be the case in the open plains of southern Ukraine, where many believe Ukraine’s likely imminent counteroffensive will focus.

In the hillier terrain of the east, the pilots could hug the ground until the last moment and then “pop,” just as they attempt now in their elderly MiGs and Sukhois, according to Venable. That means climbing suddenly at a 30-degree angle and experiencing four or five times the normal force of gravity before taking their shot and diving again for cover. But the chances of success with a single missile are limited and additional jets would be exposed after the initial surprise.

“You aren’t going to be hitting anything,” Venable said.

Some Ukrainian goals for the F-16s, such as shooting down cruise missiles, are indeed impractical, says Dan ‘Two Dogs’ Hampton, who flew 151 combat missions in the jet during the two Gulf wars and Kosovo. That’s because there’s only a short window between when a radar detects a cruise missile and the moment it reaches its target. For an F-16 to succeed it would need to spend too many precious flying hours circling in wait.

But he’s more optimistic about how they’d fare against Russian air defenses. They’d be a tough challenge, Hampton said, but a lot depends on how well integrated they are. The S-400s were developed to defeat 4th generation aircraft like the F-16, “but they aren’t magic,” he said.

Hamilton is far from alone in thinking F-16s are worth sending. They would offer a clear signal of long-term allied commitment, important both to Ukrainian morale and as a signal to Russia’s President Vladimir Putin, whose strategy in Ukraine now appears to rely on outlasting the West’s political will to arm its defense.

Another clear benefit is that Ukraine’s air force is struggling to supply the parts needed to keep its remaining Soviet-era planes in the air. F-16s would have value just as replacements, essential to keeping Russia’s still large and dangerous air force at bay.

Some also argue that if supported by a ground-based and integrated system of radar, layered air defenses and enhanced electronic warfare capabilities, the F-16s could achieve what former UK Air Marshall Edward Stringer calls a “poor man’s air superiority.” By driving back the zone in which Russian jets can safely operate, that could reduce a growing threat from the heavy glide bombs Russia has adapted for launch at front line Ukrainian positions.

They could also launch US AGM-158 JASSM stealth cruise missiles and their anti-ship LRASM cousins. Delivered in sufficient quantity, those weapons would vastly expand Ukraine’s capacity to strike targets deep behind Russian lines, in occupied Crimea, and at sea.

That’s viable, says Venable, but also expensive, raising the question of whether the hundreds of millions of dollars involved in supplying properly equipped F-16s could be more effectively spent on Ukraine’s ground-based air defenses, or other weapons systems.

JASSMs cost upwards of $1 million per missile, depending on the model, and it can take more than one to destroy a target. A single mission with four aircraft would cost at least $8 million to arm.

F-16s would need the latest AMRAAM air-to-air weapons to have a chance of out-ranging the 200-kilometer (120-mile) missiles that Russia’s — on paper — superior SU-35 jets have been using against Ukraine’s air force. Those were costed at $1.8 million a piece in the Pentagon’s 2023 budget justification.

Then there’s the cost of the planes themselves. According to a March US Congressional Research Service report, a recent sale of new F-16s to Bulgaria – including munitions and training – priced the packages at $209 million each. Older F-16s sold to Italy in 2015 cost $23.8 million.

Another concern is that the F-16’s relatively light landing gear and an unprotected air intake slung below the fuselage mean that runways need to be smooth and swept of clear debris that might get sucked up into the engine during take-off or landing. That’s a problem MiGs and other aircraft like Sweden’s Gripen don’t have.

In Hampton’s view, though, many of these obstacles are overdone to justify not giving Ukraine the NATO-standard aircraft.

“I’ve flown F-16s out of some really lousy airfields, through sand storms and ice storms. Sure it’s more sensitive than a MiG or a Gripen, but it can be done,” he said. “I’m still here.”