When must cellphones be off on a flight?

By Cruise

US Airways flight - When we should turn off our cellphones? The flight attendant is telling us to turn our cellphones. There always people that don't care about what they should do. If someone is constantly violating the rules what we need to do?
It may look like confrontation but we have to do something. If we now a violation is going on then it is appropriate to inform a flight crew member. It's all about safety.

General announcement that we know is that you may use your cellphone until the jet door is closed. We have to be obedient to flight attendants who want from us to turn off out mobile devices. Flight attendants are responsible for the passengers and their safety.
All mobile devices could do damage to an airplane. We don't know what will happen. But definitely there is a danger. There are cases when electronics do harm the systems on the plane. Respect the rules and don't be stupid.