My Macbook Air has had a persistent problem where it crashes when on airplanes. Typically, the computer will work for 10-15 minutes, then I will get the spinning colored circle cursor. I will wait for 10 or 20 minutes, but the spinning circle won't go away. I have tried powering the computer off, but it generally will not boot back up. Apple replaced the hard drive once while the computer was still under warranty, and the problem seemed to be fixed the next time I flew. However, now a few months after the repair, the problem has returned. When on the ground, the computer operates normally. Has anyone else encountered this problem? Any suggestions? Thanks!