Okay, I am no expert at airline operations, to say the least. But it could be a combination of many factors at work in last week's debacle, including the usual mechanical delays. My niece traveled on a perfectly clear day from IAD to FLL on 14JUN departing around 9am. A good day. So what did she endure? Flight left the gate on time, took off and once in the air had to turn back to IAD due to a radio malfunction in the cockpit. Creeping waits occurred and finally they were told they would be put on the equipment that was due in from Mexico City at 2pm. At 345pm they boarded the new aircraft and left the gate. They taxied to the runway and they had to return. Reason? Faulty brakes. Had to wait 30. minutes for a gate to open up. So there was a 7pm flight scheduled to FLL. What did UA do? They cancelled that flight and pulled the equipment to accommodate the 9am folks. The reason shown on the UA status for the 7pm flight was it was cancelled due to "operations" issues. She took off on the new flight a 745pm and arrived FLL around 1040pm. So I can only assume UA also had it's usual mechanical delays last week which only exacerbated the problem.