I have one of those High Sierra double ski bags, and it is acceptable, but not very robust. Lots of tears in the fabric and the zipper is pretty cheap.
I live in Arizona, but have a Fusion Pass on Mt. Hood, so I end up flying a lot (I think it was about 10 round trips last year). This season, I am buying SporTube hard case. They are pretty expensive (like $150 or so), but it is a hard fiber case - which means the airlines will actually be at fault if they break your skis. If you have a soft case and they break them, you are SOL (that is why they make you sign a waiver when you check them).