This is probably the right decision, as much as it is a frustrating one: “NATO Secretary General Jens Stoltenberg said Tuesday that European Union members will not lend fighter jets to the war in Ukraine, after days of mixed messages from officials across Europe.”
God knows how clearly Vladimir Putin is seeing anything these days, but if Ukrainian pilots are traveling to Poland or Slovakia and then flying into Ukrainian airspace to fight Russian jets or bomb Russian targets… then the Russian military would declare those Polish or Slovakian air bases are now legitimate military targets – and then the war between NATO and Russia ensues.
(As for the question of whether Ukrainian pilots know how to fly NATO jets… the short answer is, it depends: “The Ukrainian air force flies Soviet-made MiG-29s and three types of Sukhoi jets. Three NATO nations, Poland, Slovakia, and Bulgaria, also fly the MiG-29, a twin-engine fighter jet developed in the 1970s. Bulgaria also flies the Su-25, a close-air support jet also flown by Ukraine.” NATO probably doesn’t have a lot of MiG-29s, and it would be hard to begrudge Poland, Slovakia, and Bulgaria for wanting to keep their own jets for possible use by their own pilots during the crisis.)
I do wonder if a NATO country could theoretically land their jets near the Ukrainian border, have Ukrainian pilots taxi across the border line, and then take off from Ukrainian soil. Or whether NATO countries could (utterly implausibly) claim that Ukrainian pilots snuck onto the air bases and “stole” some MiG-29s.
But barring some far fetched scenario like that, the Ukrainian air force is on its own. NATO wants to help and will ship weapons across the border — but getting into a direct shooting war with the Russians could easily escalate out of control.