Nauru: Nauru is a small island country located in the Central Pacific. It does not have an airport with scheduled international flights.
Monaco, a microstate on the French Riviera, does not have its own airport.
San Marino is an independent microstate located within Italy.
It does not have an airport, and the nearest airports are Federico Fellini International Airport in Rimini, Italy
Liechtenstein, a landlocked country between Switzerland and Austria, does not have its own airport.
The closest airports are Zurich Airport in Switzerland and Altenrhein Airport in Austria.