I've had the priveledge of sitting in the cockpit during landing a number of times. The first time was coming into San Fransisco 2 years ago. Most recently, coming into Tokyo. I've never been denied a visit to the cockpit during the 'boring' bits of the flight. Just asking the FA politely normally does the trick (maybe combined with EC Gold?). What is truly special is having been able to sit in the cockpit of a 744 during takeoff from LHR 4 times and once out of NRT! I only ask when I'm sitting on the upper deck. After settling into my seat, I go up to one of the FA's, present them one of my business cards and a picture ID, normally from one of the companies I consult to prove I'm not a complete nut . And just ask if it is possible. It's worked about 1 out of 4 times.