(4)Any restraint imposed on any person on board an aircraft under the powers conferred by the foregoing provisions of this section shall not be continued after the time when the aircraft first thereafter ceases to be in flight unless before or as soon as is reasonably practicable after that time, the commander of the aircraft causes notification of the fact that a person on board the aircraft is under restraint and of reasons therefor to be sent to the appropriate authority of the country in which the aircraft so ceases to be in flight, but subject to such notification may be continued after that time-(a)for any period (including the period of any further flight) between that time and the first occasion thereafter on which the commander is able with any requiste consent of the appropriate authorities to disembark or deliver the person under restraint in accordance with the provisions of sub-section (5); or(b)if the person under restraint agrees to continue his journey under restraint on board that aircraft.
