Morning all

As a new kid on the block, apologies if I'm in the wrong place, but I'm hoping some of you experts on here can help with something that puzzles me.

Over the past couple of years I've noticed that when transiting from one flight to another in e.g. Dubai, Qatar, etc even though I have just got off a plane, I have to go through the full security screening before I can go to the transit area.If I was going to blow up the plane, where would I have got the bomb and why should I only plan to blow up a second plabe?

I'm sure there's a sensible answer, but it eludes me!!