They know their loads, they know what is going on in Europe and how that logjam is affecting travel as those flights start flying again, know what the weather will be, etc. There are some flights that can have delays over several days.

What's the on time performance of that flight, does the airline's website list it?

The government maintains statistics of the most delayed flights (though only through the end of 2009 so far)

http://www.bts.gov/programs/airline_...layed_flights/

there are some delayed over 90% of the time. One would think they would change the schedule to make the numbers better, but if they only have a certain number of slots to land and take off on each end.....