If you notice air escaping from the wrong opening while pumping, remove the AIRPORT pump head. Rotate the wheel until the valve is at the 12 o’clock position, right at the top, then reattach the pump head. If the tyre is completely flat, this alignment is particularly important to ensure the automatic switching mechanism selects the correct valve opening. This applies to Presta (SV), Dunlop (DV), Schrader (AV) and the Schwalbe Clik Valve.
For more information, see the FAQ: How do I use the AIRPORT with the different valve types?