So, I just finished High Noon, and now the only available missions on my GPS are Zero's and the airstrip. Those aren't mandatory, so why aren't the last Casino mission and the last Heist mission showing up?
You need to complete Pilot School. That's where I was stuck on before. You must get that license to continue to Las Venturas. But you're right with Zero, you don't need to complete them to get the last mission (but do for 100%)