Maybe there is more to this story or why they did that but I really, really doubt there is anything other than the fact that his name has ‘Islam’ in it.
He did advocate the death of Salman Rushdie after Khomeini put that three mil on his head. Of all the possible reasons to keep someone off a plane, “Publically supported a fatwa” sounds pretty legitimate to me.
He’s not barred from flying (since he did fly all the way from London before his plane was diverted), he’s barred from entering the US. When did that come about?
The reason that he was refused entry (according to BBC Radio this morning) is that his name is on an Israeli supplied “watch list” as he is alleged to have given tens of thousands of pounds to Hamas. He denies this.
Cat Stevens/Yusuf Islam is British, so wouldn’t have to apply for a visa, if the trip was for non-commercial purposes.
Frankly he has been extremely outspoken and quite radical in his Islamism, the zeal of the convert and all that, no doubt, and has supported some fairly iffy causes such as Rushdie’s fatwa.