International flights are 4 hours before flight time and domestic flights are 3 hours. I usually fly from Buffalo so it's the 3 hour pick up time but after having several long trips from WDW to the airport I started calling the day before and requesting an earlier pick up time.....I ask for 30 minutes earlier. If you are lucky and your bus picks you up and then goes straight to the airport the 3 hour pick up is perfect but I had three trips in a row that I was picked up and then the bus made 1-3 other stops before leaving the property for the airport. The time that is was 3 stops I arrived at MCO only about 70 minutes before my flight. That's just way to close for comfort, it's a very busy place even on a slow day.
The last time I used DME to get back to the airport I booked my earlier pick up and the driver was late, then we made another stop and at that stop there was one large family (approx. 15 people) that was not ready to board the bus. They were not all at the stop waiting, they had several strollers that they needed to unload and fold up, they wouldn't get on the bus until all their stuff was loaded underneath, etc, etc. This stop was over 20 minutes. Kudos to the driver for keeping his cool and being patient. We then arrived at the airport with less than 2 hours. Fortunately we didn't have any bags to check but the security line was the longest I've seen and took 45 minutes to get through.