One point that CARD said that I agree with is the clearing house. However for what I have been told for years is that the airline doesn't receive the total on the ticket or the portion flown. What they do is take all the US or UA
tickets and weight them. A certain weight of tickets brings more money. All the airlines who accept FIMS or the flight coupons have agreed to this method. A FIM is FLIGHT INTERUPTION MANEFEST, if UAL cancels a flight DEN
and you have to take DL DEN
then a FIM will be issued and the price is already negotiated for the two carriers. That is why you will see an airline like AA
taking tickets from lets say HP
for $150.00 round trip, and their fare is easy $250.00 it is because they get paid a set price.
Hope this helps a little.
ual 777 contrail