MEL - when have you dispatched ??

[Max Angle]

I believe the correct legal definintion in the UK is "when the aircraft first moves under it's own power for purpose of taking off"

In bmi the company policy was that the MEL applied until you started the take-off. If you had a problem during taxi you could not disregard the MEL, you had to return to the gate and get if looked at, fixed, carried forward or get off it was a stopper.

We have now reverted to using the legal definition but I think common sense still comes into it, if it's something thats going to ground the a/c downroute or a major failure it's clearly better to gi back to the gate.