A month into Russia’s invasion, “one of the biggest surprises of the war in Ukraine is Russia’s failure to defeat the Ukrainian Air Force,” The New York Times reports. “Military analysts had expected Russian forces to quickly destroy or paralyze Ukraine’s air defenses and military aircraft, yet neither has happened.”

Russia invaded Ukraine “with an arsenal of advanced fighter planes, bombers, and guided missiles, but significant combat losses in more than three weeks of fighting raise questions whether Moscow will ever fully dominate the skies,” The Wall Street Journal adds. How did Ukraine’s Soviet-era fighter jets and air defense systems deny Russia aerial impunity? 

First, Ukraine has been nimble and creative with the air defense systems they have, a mixture of decades-old S-300 long-range missile-defense units, Turkish Bayraktar TB-2 drones, and portable U.S.-provided Stinger anti-aircraft missiles. Ukraine’s long-range anti-air batteries have forced “Russian pilots to fly lower to escape those systems, but that put them within range of the shoulder-fired weapons,” like the heat-seeking Stingers, the Journal reports. The heavy losses inflicted by these weapons have limited Russian sorties.

Second, despite having only about 55 working fighter jets, Ukraine utilizes its home-field advantage. “Ukraine has been effective in the sky because we operate on our own land,” says Ukrainian Air Force spokesman Yuriy Ihnat. “The enemy flying into our airspace is flying into the zone of our air defense systems.”

The Russians “have almost full air superiority,” because Ukrainian has limited air defense and aircraft, a Ukrainian fighter pilot using the call sign “Juice” told CNN’s Anderson Cooper on Monday. But “Russians have a lot of losses, and they have a fear of our air defense.”

Third, in the eight years since Russia annexed Crimea and stealth-invaded Ukraine’s eastern Donbas region, “we have developed different techniques to give the enemy a punch in the teeth,” Ignat tells the Journal. Ukraine’s air defense has also likely “benefited from new approaches to fighting that the military embraced as it reorientated toward NATO and abandoned its Soviet-era centralized command,” the Journal reports.

Ukraine’s air force is greatly outnumbered, but its jets can take off from partially destroyed runways or even highways, the Times reports. “I only have to use my skills to win,” a fighter pilot name Andriy tells the Times. “My skills are better than the Russians. But on the other hand, many of my friends, and even those more experienced than me, are already dead.”