“First, as has been said elsewhere, have you ever heard of "XYZ airlines apologises for the late departure of Flight 123 for Wherever because the flight and cabin crew were delayed by train/car/other delays"
Err, Yes.
Flight back from Budapest, over an hours delay waiting to get on the plane, then over an hours delay sat on the plane waiting for a new take off slot.
The reason. There was a meeting of senior NATO officials in town that day, and as a security measure large sections of the motorway system were closed down. Result traffic chaos, result the crew were delayed getting to the airport from their hotel.
Now this has only ever happened to me once, and I am sure that this sort of thing is very very rare. But it does go to show that being late can happen to even the best of us.