Part of security is the psychological aspect, both for the potential terrorist and for the public you're trying to protect. A tank is a big "we're here" sign.

I don't think anybody will bother "nuking" an airport. They'd much rather have it detonate over central London (for maximum damage and casualties)...if they ever got their hands on such a weapon it would be a terrible day.

With the weapons they do have, they want to make as big an impact as possible. Using a shoulder fired missile to take down a plane load of people is unfortunately a lot of bang for the buck.

Keep your head down,