Share your experience!
Usually I set the flight mode (phone and wireless interfaces off) at night.
While in this status, the phone still synchronizes itself with my office exchange server and i find new emails when I wake up, with the phone still in flight mode. It happens only with the exchange account, google mail or play store apps are not updated.
Do we risk a plane crash? 
The phone should not have any daya connection whilst in Flight Mode. If this does occur then I would first of all suggest a software repair on the phone, This can be done via the PC Companion. If this does not resolve the issue then the phone would need to be examined. To arrange this you would need to raise this with your local support team http://bit.ly/wPKtf6
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I have noticed the same behaviour, received emails via exchange when the phone is in flight mode.
Also if I look at the powermanagement there seems to be some activities during flightmode that sometimes decreases the battery very much. Repaired the phone several time thru SUS.
Did you solve the problem after SUS?
Just to add that if Extended Standby Mode is enabled there is no email activity.
Does the software repair reset phone settings?
No the issue has come back. But it happens very seldom, only sometimes each month. Next time it happens I will try to remember to do some deeper troubleshooting.
If it happens often for you, try to do a SUS restore and then do not install any apps for a couple of days to see if the problem is gone for you.