Happened to me twice on my India trip. Once on Jet Airways 737-800, it was quite empty, moved and me and my parents got separate rows where we could sleep for an hour. For me and my mom, we were lucky on Emirates A330 from Kolkata to Dubai, was seated on 29K (had that row to myself) and my mom was seated on 30K (had that row to herself too). Surprisingly, CCU to DXB is somewhat empty, but in mid flight we managed to get 4 seats to sleep on in different rows. Helped a lot. I'm surprised EK flies 2 planes to CCU each day, which are both A332 just like Trivandrum. And back in March 2009, when my mom flew herself on Emirates's 77L from SFO-DXB, she had 3 seats to herself and found a four seater to herself during the 15 hour flight. This is the only time this has ever happened to me, every other time, flights are near full in my observation.