It's been more than 50 years since commercial flights from the United States could legally land in Cuba, and now domestic airlines have under two weeks to explain to federal regulators why they deserve to have a few of just 110 daily round-trip flights to the island.

The battle for Havana will be particularly fraught because the agreement to restore commercial flights includes only 20 slots in the capital.

American Airlines, which flew 1,200 charters to Cuba last year, the most of any U.S. carrier, will request daily flights to the island from its hub in Miami. Delta Air Lines said this week it wants to fly to Havana but did not specify any U.S. departure cities. Those are the only publicly proposed scheduled services by U.S. carriers so far.

JetBlue Airways Corp., which has built a "focus city" in Fort Lauderdale, Fla., is likely to request a flight from there and possibly one via Tampa and New York. United Continental may seek to fly from its hubs in Houston, Chicago, and Newark, N.J.

This process of gaining authority to fly from the U.S. to the 10 international airports in Cuba will culminate when federal officials dole out access based on an effort to "maximize public benefits," the Department of Transportation said in its announcement this month.

The return of commercial flights between the U.S. and Cuba, which could occur as soon as this summer, will remain restricted to one of 12 permitted activities — and tourism is not among them.

To win a route, in other words, the carriers can't press the public interest in Cuban beach vacations. The U.S. allows travel to Cuba for such things as professional meetings, athletic competitions, religious activities, and humanitarian projects.

It's not clear whether carriers with established charter flights will have any advantage. JetBlue currently flies charters from three U.S. cities to Havana and Santa Clara, Cuba. "I think it's safe to say that the Havana market application pool will be oversubscribed," said Rob Land, JetBlue's senior vice president of government affairs. It's far less clear how much interest U.S. airlines will have in the nine additional Cuban cities that will now be open to them.