Is there any way switch on/off flight mode programmatically in Windows Phone 7.5. What I want to do is create background task which will be check time and switch on/off flight mode.
Thanks in advance.
No, this functionality is not available.
It was a design principle behind the platform that applications should not be able to do things without the user knowing it.
If such functionality was available then it would be possible for an app (either deliberately or accidentally-though a bug) to get the devices state in a setting other than what they user may expect. In such a scenario users will typically blaim the phone/platform for what has happened, not a misbehaving application.