Which countries in the world do not have an airport?

Of all the countries in the world, as of now, only five countries do not have an airport within their borders.

All the countries are in Europe, they do have a heliport, and are all dwarf states.

Which countries do you think don't have an airport? The following countries don't have an airport.

1. Andorra

2. Liechtenstein

3. Monaco

4. San Marino

5. Vatican City

Which one can you reach by sea?