If you don't want earphones that fit inside the ear-canal and block sound (IEM), consider the Audio Technica AT-ANC7.
I replaced my Bose QC-2 with these, and after about 100-150 hours of burn-in they are sounding pretty good - and the batteries seem to last forever. I have a small portable air conditioner in my bedroom, and when I lay down in bed with music playing these will completely make the AC disappear. And, I can still hear the alarm go off in the morning, which I can't hear when I have a small earphone crammed in my ear canal. On a plane with the AT-ANC7 you could tell when your neighbor or the steward(ess) is trying to ask you something, but not have the roar of the engines get in and ruin the music.
If you do go with an IEM, good sounding small ones that block sound very well include the q-JAYS, IM716, ER-6i, ER-4P, and Shure SE310 through SE530. My top recommendations for "bang for the buck" would be the Shure SE310 or q-JAYS. The Shure are more likely to not need an amplifier and still give you good bass, while the ER-6i do best with an amp that has bass boost, and the q-JAYS, IM716 and ER-4P will probably need an amplifier on the plane. I used the IM716 on a plane last December, and my iPod touch volume had to be cranked up very high because they do best with an amp. The ER-6i did not have that problem on a plane, but I heard almost no bass while listening on the plane through the iPod.