Well a VERY long day at work has given me a good gauge of true battery life. My iPad is running almost all day playing videos, checking emails, and surfing the internet. My iPad has been being used since 7:15 this morning and it is now 12:30 am and I still have 14% battery left.
The 10 hour barrier has been shattered and I'm moving into 16 hours usage today. Shouldn't be a problem on any flight...even international