The Florida Keys Marathon International Airport is a public airport located along the Overseas Highway (US1) in Marathon, in Monroe County, Florida, United States. The airport covers 190acre and has one runway.HistoryMarathon Airport was originally constructed by the United States Navy in the early 1940s as Outlying Field Marathon (OLF Marathon), an auxiliary airfield to Naval Air Station Key West. It was deactivated as a military facility at the end of World War II and transferred to the government of Monroe County for use as a civilian airport. For most of its existence, the airport has been a general aviation facility. Regional propeller service began in the 1960s with National Airlines treating it as a flag stop. Later, American Air Taxi (AAT Airlines) ran a limited passenger service into Marathon. In the late 1960s Southeast Airlines serviced the airport with three flights daily to and from Miami, via Key West, utilizing two Martin 4-0-4s and a Fairchild F-27. After the demise of this service, an airline founded in Key West (Air Sunshine) serviced Marathon with Douglas DC-3 aircraft to and from Miami. For a time in the early 1970s, Air Florida provided service to Marathon and Key West, followed by Provincetown-Boston Airlines (PBA) which used a combination of DC-3s and modern turboprop aircraft.