I would get a ski tube for sure. I have a ski bag and a soon a ski tube. Why you may ask? I fly Northworst (Northwest Airlines). First off they will only reimburse you if your bag is completely lost or stolen. They will not reimburse you anything for broken or damaged equipment which is BS. I found this out the hard way with a friend. Also, it is a policy of Northwest to only cover up $2500 dollars of equipment. So if you carry two pairs of skis and a high end pair of boots, poles, accessories that $2500 can be burned up really quickly. Not, to mention they are a pain to deal with claims......I mean a real pain.
I ship my skis to Colorado every winter via UPS and have them insured or I just drive out there now. When I fly I only take one pair of skis with me and then have my boot bag as my carry on.
Just my friendly advice.