This is a clear weakness of airports: where people regroup even before reaching the terminal, with no surveillance or security checks whatsoever. And that's not just in Brussels.

But why should checkin areas be more protected than any bakery, bus stop or supermarket, any place where people gather. One can't (and shouldn't) put policemen at every corner of every street.

And of course not just in airports. Train stations, buses, markets, theatres, concerts (Balaclan), anything you have in city life where people gather together.

Metros and mass transit are generally the most lucrative target, as we see here, and as we saw in London 10 years ago.

Only place I've seen some security checks was at Ben Gurion airport in Tel Aviv, where there was a mild security check when entering the airport.

This consisted of a small interview on what I've been doing in Israel, where I am going to, with whom and who packed my stuff. This all was before even entering the actual terminal building.

I see Europe in the future adopting many of the (some call paranoid) security measure of Israel. For example security checks before entering all malls.

In Paris, there are security checks at entrances to malls and big stores now.

Yeah I don't think this is easily mitigated short of increasing throughput through check in / security so that you never have large groups of people standing around.

I traveled through Baku airport in Azerbaijan last summer which had body and luggage scanners at the entrance to the terminal. I wonder how long before this becomes the norm?

This really won't help the issue. You still create choke points where many people are waiting to pass through the security check.

People interested in killing others will just go for the easiest place, so they will just bomb the line at the scanners entering the terminal.

I talk to a lot of frequent fliers, and almost every one of them has said that there is no point to a terrorist trying to bomb a plane any more. The easiest target for terrorism is simply the insecure portion of an airport. We saw this today in Brussels.

Get dogs trained to detect explosives patrolling all areas of the airport and I'm not sure what they're called, but they have these sniffer devices at the CN tower where they basically make you walk through a large hairdryer and it sniffs the residue blown off you for chemical signatures. It's not perfect, but a combination of those two things any place where you have large volumes of people congregating would surely yield an above average result. The dogs alone I would wager would be an efficient response - they're portable, don't take up much room and can clamber over all kinds of obstacles.

A malicious person will always be able to find a public space with lots of people. A public square, schoolyard, mall, busy street, library or whatever.

Besides, to defend against suicide bombings, the dogs would have to encounter everyone before they enter the airport checkin area, otherwise the bomber could just detonate once the dog start barking (or whatever they do to mark that they've found something).

Perhaps, but then bombs could just be detonated in open public squares, playgrounds, etc - it's actually surprising they're not.

Indeed, you cannot protect any place when more than a few people gather.

You have to stop the issues at their source: why did people who were born and raised in Europe radicalize in just one or two years? And why did the community they lived in not see or report that this was happening?

While I agree, I think we can admit that doing so will take some time. Would it not be appropriate to have compensating controls in the meantime?

The trouble is, temporary compensating controls have a history of becoming permanent once in place, so you need to be absolutely sure you want those controls forever.

That's a good point, and while I hesitate to think about this terms of pure risk management, the same stuff happens in my company.

Indeed, the explosions were in the checkin area. I was there last week and there's a couple of armed soldiers in the area, but you can walk right in without any security screening.