The first bus usually starts around 9:30AM, but it does depend on when the ship is cleared and people can start disembarking. If the Magic/Wonder is severely delayed, there probably will be a delay at the airport for the busses leaving, as they start their day at Port Canaveral. I overheard a CM complain how people were complaining that the busses weren't ready at 9AM, she then said to the other CM, they just don't understand the bus has to leave Port Canaveral, unload all the passengers and luggage, get double checked by the driver to make sure nothing has been left behind, then it can be re-dispatched to drive out the new passengers.