Or, more specifically, just 'take-off'.

The safety briefing states that electronic gadgets should be kept off "whenever the engines are running on the ground, during take-off, approach and landing." Most of those are clear enough, but I just wonder where 'take-off' ends and mere 'flight' begins.

For years I have refrained from all of this until the seat-belt signs go out, but last night said illuminated lights didn't darken until well into the flight. According to the cabin-crew I was fine to plug into some music, so I just wondered what defines the limit of take-off?