Occasionally you will find that there are no trains at all going from or to Schiphol Railway station because for instance the tunnel is blocked, a switch is malfunctioning or maintenance is carried out (usually during the weekends). In these cases you can always rely on a bus or metro to get you to one of the other railway stations in Amsterdam and continue your journey from there by tram or train.
You are at Amsterdam Central Station and no trains leave for Schiphol.Leave the station at the front and take tram 5. This line takes you to Station Zuid (South station) where you change to bus 310. This bus takes you to Schiphol. The entire journey will take you less then 1 hour so you just need 1 disposable ticket.
You are at Schiphol and no trains leaves for Amsterdam.Take bus 310 to Station Zuid (South station). From there you continue your trip from there with tram 5 if you are not pressed for time or Metro lines 50 or 51 to take you to Amsterdam Central Station quickly. Alternatively you can take bus 69 to Station Sloterdijk and continue your trip from there by train.
During maintenance weekends NS runs special buses between Schiphol and Sloterdijk station. These buses will leave from platform B13- B15 in front of the Arrivals building.