You can use a Florida Keys airport as your jumping off point for a Florida Keys vacation, though most flights that originate outside the state of Florida will connect in the Miami International Airport. A number of major airlines have regularly scheduled flights to the keys, and Key West International Airport and the Marathon Florida Airport are the two primary choices you have for these. Several small carriers fly directly to the Keys from major cities in Florida and the Bahamas. However, even if you are coming from the Bahamas, you will need to pass through customs and immigration in Miami.
The Marathon Florida Airport is located approximately 120 miles south of Miami, and the Key West Airport is located roughly 180 miles south of Miami. Even if you have chosen car rentals as your method of transportation, you still pretty much have to drive through Miami to get to the Keys. You can't really avoid this, as the entire southwest corner of the state is taken up with the extensive wilderness area that makes up the Everglades National Park and the Big Cypress National Preserve. The only way onto the Florida Keys from the mainland U.S. is the Overseas Highway, which is U.S. Route 1 just south of the greater Miami metropolitan area, across the bridge that leads to Key Largo. This is truly a legendary scenic drive running the entire length of the archipelago, and it includes the famous Seven Mile Bridge between Marathon Key and Big Pine Key.
There is a Florida Keys airport in Key Largo, but it is a general aviation facility serving only private aircraft and belonging to the Ocean Reef Club, one of the most exclusive of the Florida Keys resorts.
Monroe County, which includes part of the Everglades and Big Cypress Preserve as well as all of the Keys, has a long history of aviation dating back to 1913. What is now the Key West International Airport was—and still is—the hub of most of the early aviation activity, and it was a major point for flights to Cuba, which is located only 90 miles away. There were frequent flights to pre-Castro Cuba when the island nation was a prime vacation destination for many of the wealthy in the United States. The Key West International Airport has only one runway. It is not an overly long one, and because of that there are fairly strict weight limits for baggage. You should check with your airline before you pack. While small, the Key West Airport is a modern facility with outlets for car rentals and scheduled airport shuttle service to Florida Keys hotels.
The Marathon Florida Airport was originally a US Navy airfield, built in the early 1940s and deactivated at the end of World War II. Monroe County has operated it ever since. It began servicing commercial passenger traffic on regional flights in the 1980s. Today, it is hub for flights to and from Fort Myers and Naples. Like the Key West Airport, it is a small facility but still has car rentals as well as shuttles to many of the Marathon Key hotels and resorts. Both facilities also have charter services for seaplanes and other aircraft for sightseeing flights and to connect with camping, diving, and fishing expeditions.