I could see Khoianh's idea working, if it were coupled with pinto_97's idea of changing how image works, so that image (and therefore ORS) depends much more on the age of the aircraft interior rather than the age of the aircraft.
In other words:
- the maintenance cost of aircraft increases more quickly than at present, creating an incentive for players to update their fleet and increasing the depth of the second-hand market; and
- the image of an aircraft's interior degrades over time, but can be refreshed by refurbishing/replacing the interior - this could address Chrisy_P's concern about 757 and 767s being completely destroyed on ORS, when clearly there are plenty of examples of airlines refurbishing their vintage planes and providing popular services (DL and QF's 717s are another good example).
Naturally, you could tweak these ideas to make them work more smoothly in practice. For example:
- you could adjust maintenance costs, so that they increase in a somewhat exponential fashion rather than linearly, such that there isn't much of a penalty for owning an aircraft that is 12-24 months old but the cost starts to climb more rapidly after that, and/or taper the cost increase off after a while to address TWAAir's point about 255-year old aircraft;
- you could determine the image score based on some combination of airframe and interior age, reflecting the reality that even well-maintained elderly planes tend to be less reliable;
- you could tweak the delivery rates for aircraft - although airlines already hit a cap on their growth rate once they max out their delivery rates, so this isn't a new problem.
Taking a step back from the detail of the proposal, the reality is that AS already distorts reality by dramatically increasing the profitability of airlines. In my mind, it is a good idea to offset that hyper-profitability in other ways, to produce a simulation that more realistically reflects the challenges that airlines face in maintaining their profitability. In my mind, the right question to ask is whether those changes reflect real-world challenges that airlines face. I think that having to deal with an aging fleet is a realistic, real-world challenge, and so would be a good change.