Ronald Regan National Airport
Heathrow is slightly closer but there are good transport links to/from both of them.
Midway Airport
There are no airports inside the Washington DC boundary, however, there are three commercial airports that are nearby. DCA or Ronald Reagan National Airport is just across the Potomac River in Arlington VA, but it is not considered an International Airport. IAD or Dullas Airport is the next closest in Dulles VA. IAD is one of the busiest domestic and international airports in the DC metro area. BWI or Baltimore Washington Airport is slight further afield and is closer to Baltimore than to DC. It is a very busy domestic airport, but it does have international flights.
Ottawa is closer to Washington DC than Havana.
Ottawa is closer to Washington DC than Havana.
Oregon is closer.
Fort Lauderdale
O'Hare Airport is the closest big airport. There are small airports that are closer. Waukegan Airport is close.
The Los Angeles airport (LAX) is the closest major airport. Oxnard Airport is closer if you have your own plane.
Gatwick Airport is closer to Dover than Heathrow Airport. Gatwick is approximately 90 miles away from Dover, while Heathrow is about 110 miles away.
closer to what?
London Heathrow