Turning to our last market structure, oligopoly, a. Why would airline service in most U. S. markets be characterized by oligopoly? b. Some airlines began charging extra for "amenities" (pre boarding, extra leg room, blankets). Other airlines could have kept their prices lower and not followed along, but many (most) have followed along and done the same. Utilize what you have learned about oligopolies, explain why other airlines have done so rather than engaging in more competition