Basically , what they are doing is adjusting fares to match the various PFC tax charges so that no one hub is more dominant over the other in terms of fares "searches" ! so now whether you travel via DTW MEM MSP
or even CLE
codeshare partners, the fare is the same, but they had to adjust fares to accomplish this since the PFC charges are set by individual airports..It all makes sense, but is pretty hard to explain!
would actually absorb the charge in certain situations, so that certain routings of theirs were not passed over to the competition,,just over the difference of $3.00 or $4.50.
In a fare search ..people would make their decsions for that little of an amount!
Hope this explains and chime in anyone if you think I missed the point!