This subject is always an emotive one and gets some good debate points going.
I have to agree with Norman Stanley in his comment that we have done pretty well in the UK with firearms related incidents by keeping firearms out of peoples hands. Yes we do get shootings on the streets of the UK but thankfully they are minimal. Our police force have, for the whole, determined they can get about without loading themselves upto the eyeballs with firearms and I respectfully suggest that they are put in a number of potentially more dangerous situations than your average airline pilot.
If they did arm pilots I am not sure what would happen when they came into land at the UK. I can't imagine the authourities being very happy about someone bringing firearms into the country, presumably they would have to be locked up on the flight deck with a nominated person responsible (ie, the Captain).
A comprehensive training course would have to be provided, yes even two weeks under a licenced centre with expert knowledge, ie. military of police, as stated before. I think the idea of a short course by a non-military outfit, as seems to have been hinted earlier, is downright daft. You may hold a firearms cert but does not mean you are necessarily any good with it.
Currency would also have to be looked at, if you were expecting an aircraft Captain to be responsible for a firearm then you would have to expect him to be practising regulary and any lapse in this currency resulting in the removal of his right to carry the weapon. Assessments would also be required to ensure that he/she can still use the weapon in the manner in which they were instructed.
Finally there would have to be some sort of failsafe method to ensure that if the owner did lose possession of his firearm that it was rendered inoperable. You do not really want to go giving a terrorist another method of controlling the aircraft.
Maybe at the end of the day, pilots are pilots not lethal enforcers and therefore the best way to deal with this issue would be to keep it out of the pilots hands and in the hands of a skymarshall who is specifically trained in these duties. It also has the added advantage of the fact that the terrorist will not know who he is until its too late!
Maybe someone on here who with a UK police firearms unit can offer a view on what their reaction would be to civvy pilots carrying firearms onboard?
Julian.