FaceTime on the listed MacBook Air to .....?
Most likely this is about the ports the different stages in calling and Video use.
If your Modem routes or if you have a router make sure it is doing UPnP to open the required ports
Get your Contact to do the same at their end.
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously