Bit of drift, but Rigga mentioned authorisation for engine runs and taxying. Never understood why the average UK technician could be authorised to act as tug driver, brakeman, lookout and overall supervisor of a towing operation and ground running engines throughout the ground-range but, with a few exceptions (eg some training establishments) technicians are categorically forbidden to be considered for taxi approval. In my own experience;
Base Maintenance input; military scenario. Aircraft lands from operational sortie at 12.00. Debrief in the line-office. Request a tug at 12.30 to take aircraft to the ground running area for pre-check engine tests. 13.00, arrive ground running area. 1315, ground running team arrives at the aircraft by landrover, as the military tug only accomodates driver and one passenger. 14.00, ground runs complete (took 40 minutes including airframe systems tests) request tug. 14.30, aircraft delivered to Base Hangar.
Base Maintenance input; civil scenario. Aircraft lands from operational sector at 12.00 Debrief at the aircraft whilst passengers disembark. 12.15, engineers start and pushback, taxi to ground running area. 12.50, ground runs complete (took 20 minutes because airframe systems test completed during taxi). 13.00, aircraft delivered to Base Hangar.
I think it's one of the areas where military legacy attitudes have inhibited the general leap forward in efficiency of maintenance operation.