Originally Posted by
Often1
The only way an IDB ought to occur after boarding under the post-Dao rules is not through overbooking but because a seat goes INOP, heat suddenly takes the MTW down and so on. In that situation, the entire aircraft would be offloaded and then all but the IDB would be boarded.
UA only needs to have its IDB order established prior to the flight and available for later DOT inspection.
In the recent 2017Q2 announcement, UA stated IDB is down 80% versus a year and a year ago UA was below the industry average.
So a rare even has gotten even rare.