First of all, if You intend to use fAircrack to illegal purposes - despite developer's (kindly asked) will i nthat matter - we don't want to talk with You

Second, if You got problems at this stage, You should definitely stay away - for now - from things like aircrack-ng. Google for it's website, educate Yourself, and then try again - preferably, on your own router, instead of harassing other's people private networks.

/Estel