I would go with a pair of noise reduction earphones for flying. From all my Web research, Shures tended to be rated higher by users than Entymotics.

I bought new Shure E2c's sound unheard on eBay. I have been happy with them so far. I will probably upgrade to E3c's eventually. You really have to wedge the E2c's in pretty tight to get the best sound and noise reduction. Aesthetically, I think the E3c's are a better match for the iPod since they are white and I think the third style of rubber sleeve is the most comfortable (I tried my friend's).

I also bought a pair of Sennheiser PXC-250's and I use them around the house since I find them easier to use on a casual basis. They don't deal well with voices on an airplane, weigh more and take up more space. Other than that, I think the sound quality is very good too. It's all personal preference.