I work for PricewaterhouseCoopers. We are global and since Consulting is a large part of our Business, there is a lot of travel involved. The reason for the Airline restriction is becuase of special discounts and benefits that are exclusive to our agreement. Occasionally if there is a much cheaper fare or no reasonable direct route, we can fly a non-preferred Airline, but those instances are rare.
Thanks for your thoughts so far!