Look guys, SLF here, get over your hysteria please. 20 were killed in Brussels metro, 11 at airport. Nobody is talking about doing security checks of every passenger in the underground systems in the world's major capitals. Being stuck in a strongly confined space with an explosive set off by some idiot tends to be deadlier than a wide open space. Also, if you have a security check, invariably there is then the crowd in front of the security check ...
The reason why people want stiff security checks for planes is not for the sake of the passengers, it is because Ben Laden turned the planes themselves into weapons. Plane hijackings are old hat.
Edmund