UPS Airlines eliminate mixed fleet reducing multiple manufacturer spare parts, engines, and training.
UPS has both PW and RR engined aircraft for 757 fleet. Sell them off to eliminate having two different engine types with spares reducing parts inventory. Replace with more 767's that have one engine type.
Sell off the MD-11's. Again two different engine types in the UPS fleet. 3 engine aircraft. Replace with a combination of more 767 and 777 aircraft. This will reduce parts and MX costs from going to 3 engines to two and not having to carry two different engine types for the same aircraft. It will also replace the MD-11 with more fuel efficient aircraft with better range.
Sell off the A300. Replace with more 767's. A300 doesn't have the range of the 767. Very very few interchangeable parts with the 767. Less lift than the 767. This will reduce parts inventory, reduce MX costs. Reduce pilot training for different aircraft. Better aircraft utilization. The 767 can reach Europe and Asia from the US along with domestic routes.
Sell off the 747-400. Replace with the 777. Save money by going from a 4 engine to a 2 engine aircraft. Reduce parts inventory with engines. More fuel efficient and better range. A little less lift than the 744. Can add more flights frequencies to improve customer transit times. Able to skip the ANC tech/fuel stop from Asia improving transit times.
The entire UPS fleet would be based on 2 aircraft. The 767 and 777 aircraft. Less parts inventory. Less MX cost. Less type rating and training for pilots going from 4 type ratings to 2.