Scroggs is right, most airlines have totally banned flight deck visits during flight. However, if you are wanting to ask a few questions and get a pilot's perspective, what to do is ask the ground staff at the airport you are flying from, they can get the dispatcher to see if you can board an extra 5-10 minutes ahead of the rest of the punters, so you can have a little look at the flight deck and a chat before departure. You will tend to find (with a couple of exceptions to the rule.......) that most pilots will be willing to accomodate you. Have a good holiday