If that's your plan stay clear of airlines. This has been an unusual cycle of upward movement because the US industry has finally been rationalized and for the first time EVER making reasonable profits. However, each company has also started low coming out of bankruptcy, then let the market, rational or irrational, assign it a general target. I think those targets have now been reached so airlines are not going to be moving your money to much greater heights.
And the notion of buying low and selling high is great in theory, but if we all knew when to buy and when to sell, we'd all be well set today. The market is rigged against the little guy. From time to time you might luck out buying an AC or AA when it comes out of bankruptcy and does its climb. Most of the time, you'll get creamed.