The A380 is the enormous double deck four engine super jumbo jet, biggest one in the air. It's been on the market not very long, and sales have been mediocre at best, 318 delivered or on order since the rollout. Now Airbus is talking about re engining it. The newest engines can save 5 to 10 per cent on fuel consumption. So far, only Emirates is pushing for this, they say they will take 70 more A380's if Airbus reengines them.
Cost quoted for the engineering is staggering. They are talking about $2.5 Billion just for the design, and presumably some flight testing. Wow. This is a airplane with the four engines in under wing pods. Changes would be confined to the engine pods. Design a new bracket to fit the new engine. Make some changes in fuel piping, electrical harnesses, and the pod to accommodate the new engine. You don't have to change anything in wings or fuselage or cockpit. You might have to replace the engine alternator control box, the one that keeps all four alternators in phase. I figure 4- 5 engineers, with CAD/ CAM could do the drawings in a couple of months. Then you have to test fly the aircraft to make sure everything works, and to make the regulatory agencies happy. I'd budget $200,000 for engineers salaries, and let's say $1000 per flying hour for test flights. Call it 500 hours of test flying (gross overkill) The whole design and test effort is less than $1 million. I may be a little low, but there is a helova long way between my back-of-the-envelope estimate and $2.5 Billion.
And, with the price of oil down by half since last summer, the urge to buy fuel efficient aircraft has presumably eased off a bit.