Every one of them except Israeli nationals and those who bothered applying for a Schengen VISA and actually got it.
Which, in turn, makes me wonder how they would cope with the restrictions if they have to fly to a non-UK destination as part of their training?
Crew members are generally exempt from VISA requirements (but might not be allowed to leave the airport's sterile area), but does this apply to students/trainees as well?
Ciao,
DG800
Edit: I'm referring of course to Middle East students only.