BRUSSELS—When Ibrahim El Bakraoui blew himself up in the Brussels Airport check-in area, killing and maiming scores of travelers, it was at least the third time he had passed unimpeded through an airport terminal in recent months.
Suspected by Turkey of being a “foreign terrorist fighter” and known at home in Belgium as an ex-con wanted for parole violations, Bakraoui was still allowed to board a commercial airliner unaccompanied last summer, flying freely from Istanbul to the Netherlands and disappearing without a trace.
The ease with which he did so raises questions about how much governments know about the movements of returnees among the 5,000 home-grown jihadis who have trained and fought in places like Syria or Iraq. Many now pose a “serious threat,” according to the police agency Europol. Some, like Bakraoui, have already used their deadly skills in cities like Brussels or Paris.
