The only guide I apply is that the first flight of the morning is likely to be on stand and depart, all things being equal, reasonably punctually. Any knock on effect from earlier delays always is more likely to impact later departures, however there is padding to the schedules and LCC's are very keen not to be on the ground as much as possible.
Like the stock market the past performance is not necessarily indicative of the future, but U2 are pretty good when dealing with circumstances within their control.