In 2015, the U.S. Department of Justice was investigating whether the four major U.S. airlines were colluding by restraining increases in capacity with the goal of avoiding price cutting. An airline industry analyst commented on the investigation, "I don't sense that the executives talk to each other. They actually hate each other, truth be told. But with so few of them left, there's almost a natural oligopoly."
a. What does the analyst mean by "a natural oligopoly"?
b. Would it be necessary for the airline executives to talk to each other to collude? Briefly explain.