If you politely ask the First Class/chief Flight Attendant in the middle of the flight, s/he will probably ask the Captain and you will have a good chance of going up for a look around. You are a First passenger, so just don't look too insane and you will have a good chance. Explain your interest in aviation and the dream you had as a little kid in becoming a pilot. Once you get up, if you are polite and gracious to the pilots, showing that you know what's going on without being too pushy, you might be invited back to landing. My uncle was on a BA flight a couple years ago and asked to go to the cockpit midflight. He had an intersting discussion with the pilots about various issues at the time (ETOPS, etc.), and they were impressed that he had a clue what was going on in the industry. Yes, he was invited back to the jumpseat for landing at Heathrow for the "time of his life". I'm jealous. Extremely!