In the Airport Delays Page (for a given airport), how do you define 'On Time', 'Late' and 'Very Late' in the Airport Delay Index?

'On Time' is the percentage of flights over the last 2 hours that have actual departure[arrival] times no more than 15 minutes later than their planned departure[arrival] times. 'Late' is the percentage of flights over the last 2 hours that have actual departure[arrival] times more than 15 minutes and less than 45 minutes later than their planned departure[arrival] times. 'Very Late' is the percentage of flights over the last 2 hours that have actual departure[arrival] times more than 45 minutes later than their planned departure[arrival] times.