Consulta para unir dos tablas

Si el FK en Posts.*_Airport_code no se refiere a Airports.id como asume MJB pero para Airports.Airport_code entonces

SELECT
  APS.Airport_name AS Source,
  APD.Airport_name AS Destination,
  Posts.date_of_departure
FROM Posts
  INNER JOIN Airports APS ON(APS.Airport_code = Posts.Source_Airport_code)
  INNER JOIN Airports APD ON(APD.Airport_code = Posts.Destination_airport_code)