You can't just organise the handling and transportation of passengers at the flick of a switch. As said earlier, if the airline don't have a handling contract with anyone then ringing around and finding someone able to handle the aircraft will take a while. If they do manage to find someone willing to do it, they'll be put to the back of the queue until they have spare bodies available, which in this day and age, isn't very often. Likewise, trying to organise enough coaches for 300+ people is hell, and if you add poor management from AI to it all it's a recipe for disaster.