Wouldn't it be much easier for a terrorist to get a job as airport security and then allow one of his friends past ?
Do a course for a few hundred $$$, guaranteed job at the end. May have to do car parks or public events first, but getting an airport job shouldn't be too hard.
Once someone has managed to get through to a pilots job, they don't need weapons or explosives. There already is an axe within easy reach, or just wait until the other pilot leaves the flight deck.
Most security guards are polite and professional, still doing their jobs whilst causing minimum inconvenience to those they deal with. However there are some I would love to meet in a dark car park; ignorant, power mad, arrogant, rude scum who lack the social skill needed to wheel clamp cars.
Seperate lanes for aircrew, with appropriately trained people manning them. Special ID cards with finger print or iris matching would eliminate the danger of impersonation.
BTW Anyone remember the case of a fake Virgin Blue pilot a few years back ? Made the newspapers