Ukraine's fighter jet fleet is slowly growing, but its weapons to bring down Russian jets are dwindling, leaked US document shows

• Poland received permission from Germany to send Ukraine five more MiG-29s this week.
• The jets will bolster Ukraine's fighter fleet, which is still under fire from Russia's larger air force.
• But air-defense ammunition is a more urgent need, one underscored in recently leaked US documents.

Poland received permission from Germany to send five MiG-29 fighter jets to Ukraine this week, bolstering Kyiv's fleet ahead of a season of more intense fighting.

The jets, however, won't tip the scales in the aerial battle between Russia and Ukraine, and they will arrive as Ukraine and its partners scramble to find more ammunition for Ukrainian air-defense weapons, which have been vital to denying Russia's aircraft and missiles the ability to strike at will.

Berlin approved Warsaw's request to send jets to Ukraine on Thursday, the same day it was received. Poland acquired 22 MiG-29s, which had been part of the East German military, from Germany in 2003 with the requirement that the Germans approve any future transfers.

Poland and Slovakia pledged to send roughly two dozen MiG-29s to Ukraine in March. At the time, Poland's president said the first four jets would be delivered within days, and Ukrainian officials said in late March that the first Slovakian jets were already in combat around Kharkiv.

The MiG-29s will give Kyiv an airpower boost and be familiar to pilots with experience on Ukraine's own MiGs, but Russian and Ukrainian jets remain of limited use over the battlefield, as each side has air-defense weapons that have prevented the other from achieving air superiority.

"Their integrated air- and missile-defense is working pretty well, to the point where they're shooting down [each] other's aircraft," Gen. James Hecker, the commander of US Air Forces in Europe, said at an event hosted by the Mitchell Institute for Aerospace Studies on March 22.

Having more jets "is going to help" the Ukrainians, Hecker said. "This will allow them to come at different axes, which will complicate the problem that Russia has."

"Is that going to be the enabler that's going to let them get air superiority? No, I don't think so, not anytime soon," Hecker added. "The integrated air- and [missile-defense] system that both Ukraine as well as Russia have is very extensive, and it would be difficult from a US perspective to take all that down in a couple days."

Ukraine started the war with a smaller, less advanced air force than Russia and has lost more than 60 aircraft, while Russia has lost more than 70, Hecker said at a separate event in early March. Both air forces have shifted tactics and now operate farther from the front line, playing to the advantage of the Russian aircraft, which have an edge at longer ranges.

Ukraine has also adopted US-made weapons, including anti-radiation missiles that have helped suppress Russian surface-to-air missiles and extended-range bomb kits that have had "some success," Hecker said on March 22.

Ukrainian officials have requested more advanced jets like the US-made F-16, arguing they will give Ukrainian pilots an advantage. US officials have said repeatedly that it would be too costly and time-consuming for Ukraine's air force to adopt those jets and that other weapons are more immediately useful, particularly air-defense systems, which both Ukrainian and Western officials have cited as one of their highest priorities.

According to classified US Defense Department documents leaked online in recent weeks, US officials believe that Kyiv is at risk of running out of air-defense weapons and ammunition by late spring or early summer, leaving important targets exposed to Russian attacks.

Ukraine's current air-defense plan "balances limited resources to protect critical national infrastructure (CNI), population centers, front line of troops (FLOT), and other key assets," according to a summary on one document, which has markings that indicate it was prepared on February 23 and was classified top secret. Insider obtained a copy of it and other documents but could not independently verify their authenticity.

Ukraine's "ability to provide medium range air defense to protect the FLOT will be completely reduced by MAY 23," the summary says. A detailed assessment included in the document said Soviet-designed Buk and S-300 systems compose 89% of Ukraine's defenses for targets above 20,000 feet and that based on expenditure rates at the time, the Buks would be expended by March 31 and S-300s by May 2.

Other systems, such as older Soviet-era SA-3s or Western-provided NASAMs, are limited in number and "unable to match" the volume of attacks.

Short-range air-defense weapons provided by Western countries, like Stinger missiles or the Gepard cannon, "mitigate the expenditure" of other surface-to-air missiles but "do not have the same deterrent effect" on Russian aircraft. Ukraine also has "limited to no" air-to-air defense, the document says.

Without the threat posed by those interceptor missiles, Russian aircraft would have greater freedom to attack Ukrainian aircraft and bomb Ukrainian targets, including in support of Russian front-line troops, the leaked document says. Russia's long-range missiles could also be more accurate, as they would no longer have to dodge air defenses, and the Russian military could expand the type of munitions it is using and conduct a greater range of aerial operations, further challenging Ukraine's ability to mass forces to conduct attacks.

The document suggests several courses of action, including resupplying Buk and S-300 missiles over the following three months and restricting their usage to Russian tactical aircraft. The document also suggests "military deception" and adjusting firing doctrine to counter Russian aerial attacks more effectively.

The document further recommends over a three- to six-month period providing more Western-made air-defense systems, like Patriots, and expediting work on something called the "FrankenSAM," which may refer to a modification of an existing weapon or weapons.

The document echoes many of the warnings by Western officials and experts, who have cautioned that without sufficient air-defense ammunition, Ukrainian infrastructure would be more vulnerable, its forces more exposed, and Russia's military more free to use its aircraft and gather its forces for renewed attacks.

Western countries have made air-defense ammunition a focus of recent security-assistance efforts, a reflection of broader efforts to support Ukraine ahead of an expected counteroffensive in the spring and summer.

On March 15, nearly 50 countries participated in the 10th meeting of the Ukraine Defense Contact Group, during which air-defense systems were a major point of discussion. "A broad mix of air-defense systems have been promised, and they will protect the skies over Kyiv and the free cities of Ukraine," Gen. Mark Milley, chairman of the Joint Chiefs of Staff, said after the meeting.

On April 4, the US announced a $2.6 billion package of security aid for Ukraine that included ammunition for the Patriot system the US provided in December, which will come from existing US stockpiles, as well as ammunition for NASAMs, gun trucks and laser-guided rockets to shoot down drones, anti-aircraft ammunition, and air-surveillance radars, which will be ordered from the US defense industry and take longer to deliver.

The dozens of countries at the Contact Group meeting "responded" to the challenge and were able to provide "a lot more surface-to-air missiles" to Ukrainian forces, Hecker said on March 22, "but it's something that they're using constantly because of the tactics that the Russians are using."