Last trip HKG-SFO-IAD after boarding in HKG was sitting in UD and decided to see if I could take a quick picture of the cockpit for my young boys. Pilot and F/O could not have been nicer, invited me in, had me sit at the controls and snapped a couple of pictures for me to text to the boys (the only bummer was the sun shades were still up). Pilot took plenty of time to talk and showed me the crew rest area.