If U.S. Justice Department approves the US Airways-AMR deal, Cramer noted that the entire airline industry will be controlled by just three major carriers. If Southwest, the next biggest carrier, is counted, then the top four airliners will account for more than 80 percent of passenger revenues by volume, Cramer said.
Meanwhile, Cramer said it's more difficult to enter the airline industry. Higher fuel prices leave less money to borrow for new planes, he said, while aircraft makers Boeing and Airbus have so much demand, they can't make planes fast enough.
So what's the best way to play the airline oligopoly?
"I like the three big boys the best: Delta, United Continental and especially US Airways," Cramer said. "Although up here, I think you should wait for a pullback before you pull the trigger."