Ten weeks into Russia’s wider war on Ukraine, Kyiv’s tiny, aging air force is in much better shape than anyone should have expected prior to the invasion. Videos that have circulated on social media in the last week depict each of the Ukrainian air force’s manned fighter and attack types, at least some of them while in action near the front line in eastern Ukraine’s Donbas region. The videos underscore what U.S. defense department officials said in mid-April: that an influx of spare parts from Ukraine’s allies helped the air force to repair around 20 grounded jets. As a...