Hey guys, just signed up to start the chatter on this issue which happened to me...
I was just messing around with the phone put it in airplane mode and then all of a sudden couldn't turn it off. I DID figure out a solution though. I went into to settings and location and turned everything on, somehow this fixed it and I could see the airplane icon and turn it off.
I'm trying to reproduce this issue and I think it rests in the software this things got. It probably happens rarely but If I find it I'll let you guys know....