I had trouble hearing my movies while using my T31 during flights. The volume output wasn't high enough (but I've had no problems on an older model thinkpad). On a whim I bought
these.
Cheap and amazing how well they work. They do block out a lot of the noise and are fairly cheap. Sony also sells a version of these style (in ear) with noise cancellation as well but I don't need that now. I think the noise cancel version was $100-200 or so, can't recall. And I wouldn't have any idea how they compare to other noise cancel headphones.
I saw someone using the Bose ones on a flight once, wanted to ask him how well they worked but I figure anyone who spends $300 on headphones and brings them on a flight is probably going to speak positively about them.
On the negative side, the in-ear style can be a bit uncomfortable for some folks and you (may) have to deal with earwax issues.