simulating real-life maintenance checks

I'm basing this idea on having read about maintenance checks (see for example https://en.wikipedia.org/wiki/Aircraft_maintenance_checks)

When I schedule short-haul flights on a new aircraft, it always occurs to me that it's rather unrealistic to have every single aircraft at your disposal for basically 20 hours a day, every day of the year. Most of the time, building in 2 blocks of 2 hour maintenance windows is sufficient, and I guess most people have their scheduling exactly the same every day of the week.

For long-haul, I kind of enjoy playing around with the puzzle of fitting planes with complex schedules, especially when a rotation between 2 airports can't be completed within 24 hours. Only then do you get close to the real world example where long-haul planes will see many destinations during any given week. But even that is not realistic because no plane is ever taken out for longer maintenance breaks.

Obviously there's no way we could manage this in airlinesim (real airlines have entire departments to do this kind of operational scheduling). Also, you can argue that the current maintenance system sort of reflects the need for A-checks, where an aircraft (IRL) will be out for let's say half a day.

But I wonder if it wouldn't be good to count some sort of a "required extra capacity" when growing an airline or with aging fleets, to account for lower-frequency but more time-intensive B/C/D-checks. For example, for every 20 short haul jets, you'd be forced to pay for an additional "reserve" plane which can be used (virtually) when any of the other 20 planes is out for a B/C/D-check.

Or, it could be done after every x months or years of service, by imposing extra costs that could reflect the virtual temporary leasing of a replacement aircraft to simulate the unavailability of a plane.

I don't think this would affect gameplay drastically, but it would add a bit of realism and potentially curb (slightly) the massive money-making (which is also not realistic) when reaching a certain scale.

(alternatively, I'd love to see extra "penalties" for large airlines who, by definition, lose some efficiency and have a different cost structure (higher overheads) due to their corporate size.

Virtual aircraft, virtual leases, virtual anything does not add realism…

I agree with you that it's virtual, but it would be an extra element, and extra elements in general make/keep a simulation game interesting.
Having said that, there doesn't seem to be a huge appetite for this :-)

Moreover this would take programming time, and programming time could be spent much better on something more important and necessary.