Anyone who has tried to book a summer airplane trip recently has probably had a bit of a shock. Gone are the days of flying cross-country for $400 or less now you're talking $500 or even $600. Bing Travel reports that domestic fares are up an average of 22 percent over last summer. But according to a new American Enterprise Institute report by Mark Milke, a Canadian researcher, this state of affairs isn't entirely inevitable. His research finds inspiration in a place that AEI, with its free-market leanings, rarely regards wistfully: Europe. "Every jurisdiction can have an ideological bias," Milke says, "and Europe, you can say, is sometimes anti-market, and anti-competition." But when it comes to air travel, he points out, the European Union has taken deregulation much further than the United States. Since 1997, the European Union has allowed European airlines to pick up and drop off passengers anywhere within the union. Meanwhile, back in the U.S., on...