Most of the time passengers are oblivious as to what carrier within the US system the are on .Coding the complaints with 9 express carries and 2/3 of the airline being express IS FUZZY MATH that is my point.
Let me set this straight...this is kinda long, but stick with me.
First of all, I know this stuff first-hand because I did it for East for years.
And when East Consumer Affairs closed, I moved to Express and handled this for the entire network of airlines before I left the company altogether. I also worked directly with West CR on the whole process. Not bragging, just establishing credibility.
At the start of every month, the complaint information the DOT sends to carriers is a confusing, jumbled mess. There is NO way it is ready for prime time, and the DOT expects airlines to sort it out. You're right: customers can't keep straight which USE flight is operated by Piedmont, Mesa, etc. let alone state whether they were on US vs USE. Unless (and we know most won't) the customer specifically states something like "I was on USXXXX PHL-ERI, operated by Piedmont, and the flight was delayed by three hours," the DOT is going to automatically assign the complaint to US if the carrier code on the flight was US or the ticket began with 037.
But read on...
CR reviews every file and looks up which airline operated the flight in question if the complaint is about a delay, as in the PHL-ERI example above. If the complaint is about an employee issue, CR determines which carrier does ground handling in that city. For example, if it is PHL, and the complaint is about an agent, CR determines if the flight was leaving from F-CON (Piedmont Employee) or elsewhere (Mainline) before assigning carrier responsibility. Then representatives from Mainline and Express review the findings and come to an agreement on the complaint code assignment before resubmitting the whole thing back to the DOT before their final numbers are run for the monthly report we're talking about in this thread.
Customer Relations (or in my day, Consumer Affairs) pours over every single complaint that comes in to determine which airline is responsible. They are the ones who "un-fuzz" the math for you and the consumer.
So, in the end, this report is as unfuzzy and as pure as possible.
This "fuzzy math" thing comes up pretty often. You'd think the folks in Tempe (or, really, in the old CCY since they didn't do it either) would have explained how complaints get assigned on the DOT's report by now, rather than relying on an ex-employee on USAV and word-of-mouth, but there it is.