A Ukrainian F-16 fighter jet, recently supplied by NATO countries, was destroyed this week while defending against a Russian aerial assault and the pilot was killed, Ukraine’s military said Thursday.

The loss is a blow to Ukraine’s government in Kyiv, partly because only about half a dozen of the planes have been delivered and only a few pilots have been trained to fly them.

The timing of the crash was unfortunate as well, coming after a Ukrainian incursion into Russia’s Kursk region that lifted the national mood this month after a long spring and summer of Russian battlefield gains in eastern Ukraine.