30 years in ATC I've done more than my fair share of cockpit flights (I'm talking several hundred) and I have never been refused. Did quite a few with Britannia (and met the Missus on one). To my surprise I was even allowed up front during an atlantic crossing with one of the major American carriers although the cabin crew went to great lengths to conceal the fact from the pax. Now days it's rare that I ask unless a flight is full. That's because I'm now too old to understand the answers to the questions I ask!!