Whether you're heading to the airport as a passenger, a family member or a tourist visiting a museum, you can easily use regular public transport.
Take the red line C metro to the Letňany terminal, where you can change to bus lines 185, 209, 376. If you are going to the airport, get off at the U Vodojemu stop , if you are going to the museum, get off at the "Aviation Museum" stop.
It takes about 45 minutes to get from the centre of Prague to the airport, the ticket costs the classic 1 eur.