Since Russia’s invasion started, Ukrainian President Volodymyr Zelensky, has struggled to get F-16s to aid his fight, over fears they could be used on Russian soil, potentially triggering an escalation between NATO and Russia. After saying Kyiv did not need the fighter jets earlier this year, US President Joe Biden reversed his objections by signaling to European allies that they would allow F-16 exports to Ukraine.
Source: wiktionary