A very cute, very fun game! No frills, just directing plane traffic. I think not being able to readjust plane routes once they've been set (or at least, I didn't experiment enough to find such a feature) and also not being able to directly see HOW faster/slower each plane color is, relative to one another, makes it a bit of a guessing game until you've thoroughly internalized the speeds.
I could take a guess, though, that PICO-8's limited input suite (^v<>xc) and internal code memory banks (there's a "token" limit, as I recall) would make it tough to just add all the little bells and whistles you wanted. It helps keep scope from growing out of control, but also can get in the way of an "intuitive to the player" (as opposed to a "concise implementation") solution to XYZ problem.
Whatever. Bravo, I say!