Originally Posted by
bitburgr
irrop = irregular operations
It's when things don't go as scheduled due to maintenance or weather issues.
Do maintenance problems count? I've always thought of "Irrops" as referring to widespread problems...a blizzard, ATC issues, etc. An isolated mechanical delay/cancellation, while inconvenient, does not really strike me as rising to the level of "irrops". A single cancellation is much different than an entire hub suffering from 2+ hour delays (for example).