We took DD to Barbados at 17 months old, so a little older, but she was absolutely fine with time difference and flight- daytime naps varied a bit for the first couple of days but slept fine at night when we got there and when we got home. Was amazed - she adapted far more easily to long trip than I expected.
Just back from Tenerife with ds (15 months). The best thing I did was book him a seat. Although it was more money it was worth it. He is quite tall for his age though, about the height of a 2 year old so there's no way either dh or I could have had him on our lap. It also meant he had space to lie down and sleep. Although we didn't experience a time difference, there was a major upheaval in ds routine but he adapted really well, much better than I thought.