For an aircraft remaining on the public cargo ramp and apron area for more than 10 minutes after the manager of the air terminal has directed that such aircraft be removed because of congestion of aircraft upon the said area, the urgency for making space available for other aircraft, snow removal, or other operational requirements, which said notice shall not in any event be given until the aircraft has been on such area for 60 minutes; for each additional 30 minutes or fraction thereof $5