UK Prime Minister Sunak earlier explained:

“The first step in being able to provide advanced aircrafts is to have soldiers or aviators that are capable of using them. That is a process that takes some time. We’ve started that process today,” Sunak said at a news conference with Ukrainian President Volodymyr Zelenskyy, after announcing Britain would train Ukrainian pilots.

Nothing is off the table and our leadership on this issue is something that we all collectively should be very proud of.”

Russia’s embassy to UK quickly warned of “military and political consequences for the European continent and the entire world” in response.

https://www.zerohedge.com/geopolitical/uk-pledges-fighter-pilot-training-ukraine-zelensky-surprise-visit