Sometimes it is just more convenient when transitioning to new fleet types to delete the old route, keep the slots, then create the new route.
This just happens way too often in the slot constrained airports that when I come back to use the slot, it is no longer there at its original time, but it shifts.
Another issue is that slot that's kept (owned with a star) is a lot more restrictive, has a lot less of an ability to be reused at other times - and unlike public slots, we don't know during which other times it can be used, except trying 12 different times.
As a possible solution, I would get rid of the stars altogether, and display the slots properly.
While I am not sure if this will solve the original problem, I think this inflexibility of owned slot could be eliminated. The way to do it, IMO, is to treat (and display) owned slots as if they were public slots. No star next to a slot at any given time. For the player, they would seemingly go back to the public pool (spread out over the times it could be used at as fractions of slot), for other players, that slot would not be visible as available.
Instead of the star, under the grid of slot and times (in 5 minute / 1 hour page), there could be 2 horizontal summary lines:
- 1st summary line would show total of slots in the entire hour (players slots would be included). This would be the equivalent of the fixed / enhanced single line in 24 hour display
- 2nd summary line would show how many slots the player owns during that hour. For the purposes of re-use, that all that matters, that there is some slot available during that hour, it does not matter which 5 minute block it is available at.
Another possible enhancement would be (after properly displaying each single line in 24 hour slot page to include player owned slots), a possible enhancement would be to expand the hour on the same page by clicking on it. Right now it goes to another page. So the 24 hour page would be one single slot page (to rule them all).