I think this would be a good topic for debate, but first, here is a link to the latest on this subject:

http://www.usatoday.com/news/washington/2003-08-25-guns-cockpit_x.htm

Personally, I feel that "undercover" law enforcement personal should be the only ones allowed to carry firearms on a public jet liner. Just because a pilot knows how to "fire" a weapon, doesn't mean he or she should be able to use one on board a plane full of passengers. There are many other considerations one has to take in account (pertaining to the subdual of a "terrorist") that only a professionally trained expert in this area would know. My question is why does the weapon of choice for the pilots be a gun? Why not a Tazor or another instrument like it be implemented instead? Think about it, a firearm spraying bullets in a presserized cabin definitly doesn't sound like the best choice.