Eastern leased three B-747-100 from Pan Am and operated them JFK-MIA and JFK-SJU. They optimistically expected to get over 13 hours a day utilization on these relatively short haul flights. We depleted Pan Am's stock of spare engines in no time. No one mentioned the common failure of the inner case. You would find a piece of the inner case in the overboard bleed screen. Those early engines were not good and the engine change crews became very proficient. To put it politely, the engines were immature and needed another year or two of development.
In a fit of insanity, the Marketing people put one of the beasts on the Air Shuttle for the Thanksgiving rush. It flew EWR - BOS. Remember that the tickets were sold in-flight, The flight was so brief there was no time to complete the sales so the aircraft would sit for almost an hour after landing to allow the complete the sales. The engines did not like flight legs of less than an hour and the inevitable happened. It had to be ferried to JFK for the engine change. The operation was not repeated for the Christmas rush.
Years later, when I was at Orion Air, we operated B747-100 for UPS. We had a celebration when the last -3 model engine was replaced by the so much better -7A models.