Planes takeoff/land only on runway

[Uldics]

As we all know, planes are quite easy to get in the air and land on every flat place. I want them only to be able to do that on runways. How do I do that in least lagging way?

I have tried to make a trigger over runway, and a trigger for every plane, which checks, if it is on runway, height < 1 and speed > 50. But if I have a lot of planes, there will be lag as there is one trigger per plane.

[macguba]

A plane will create more lag than a trigger.    So your limitation will be the number of planes itself, rather than the number of triggers.

However, to eliminate the triggers - it all helps - you could have a looping script which checks each plane.    The delay in the script could be ~2 or something, which would mean far few checks than a trigger would make.