I just joined to post a possible solution to this problem. My wife and I started to experience the airplane mode issue on our Moment's right after I applied the CL14 update.
Performing the below steps may correct the problem until Sprint performs another firmware/software update in the near future.
From your phone, go into your Android system settings and select Wireless Controls, followed by Mobile Networks, followed by System Select and change the setting from Automatic to Home Only. Reboot the phone and hopefully your problem is solved.
I've done some research and there may be an issue with the phone/firmware relaying and working with other providers (Verizon for example) and their towers. It could also be that it is simply a bug in the firmware that needs to be fixed. Regardless, setting the phone to Home Only solved the problem for my wife and I. We have been using the phone for a week or two with no airplane mode issue.
Hope I was able to help!
Nope, I've had my wife's phone on Home Only and this still happens to her phone every day! TIME TO CALL SPRINT AND GET SOME ANSWERS!
Report this issue to Sprint as described in http://community.sprint.com/baw/thread/32744?tstart=0 and http://community.sprint.com/baw/thread/32727?tstart=0.
The Sprint admins have stated this is the top priority right now and I think the above channels will be the best approach. Feel free to call after you have provided the requested information as described above!