I was leafing through the November 2012 Travel+Leisure magazine and they had a table compiled by "FlightStats" (whoever that is) showing Airline+Airport, % of flights delayed more than 45 minutes and average delay in minutes of these flights.
Not surprising, EWR is the leader. What IS surprising is that they used the actual airline instead of the mainline legacy that they are masquerading as in presenting their data:
CommutAir/EWR - 22.85% - 64 minutes
ExpressJet EV/EWR - 21.95% - 66 minutes
Colgan Air/EWR - 16.57% - 63 minutes
ExpressJet XE/EWR - 16.27% - 67 minutes
If my interpretive skills are right, these are all "UA" flights, no? Survey period was August 2011 - July 2012.