Cancelling arriving flights

Newbie.
Re Bari airport and the 2 slots for Large aircraft.
Quite often I have assigned 2 aircraft to the slots but 1 or two Large aircraft are in the landing queue.
I cannot find out how to stop these and when the timer runs out I lose the rewards for not landing them.
Any ideas please

Were these planes from another player or generic planes?

Generic.

That’s strange. This happens to me too, but only with players planes that are not my connection partners.

It sometimes happens as a timing issue. If you dont select a generic for landing quick enough (when there is a spot available) system assuming that spot is still available (because technically there is) and randomly selects another L for landing. Once the queue is clear of L’s and the spots are assigned. It should not pull more through unless you have connection from your partners arriving. Those will show up regardless of status on the available gates.
In that instance you have to balance the various timers (landing, cool down and speeding up the servicing on the planes already on the ground) to make it work

That happened to me with player planes. When I assign them, the left landing timer doesn’t convert into handling timer. For Example- I assign a plane that has 4 mins left for it to assign to a gate. But sometimes, after landing, the landing timer keeps on going and when it arrives to the gate, the time finishes.