Yes, Tony is right. Spotting from inside the terminal is absolutely pointless, as you cant even get near the glass, i dont really know how to explain it, but the walkway where you walk wont allow you near the glass.
If you find a good spot for spotting, you would be able to get some fantastic shots if you are lucky enough to get one with both runways being used.
The best airport I would have to say for spotting inside the terminal would have to be Honolulu International, as alot of the airport is open - no glass, nothing. I remember going into a Duty free shop then turning around because i heard such a loud noise, it was a JAL 747 taking off :lol: