Aircrack-ng is described as '802.11 WEP and WPA-PSK keys cracking program that can recover keys once enough data packets have been captured. It implements the standard FMS attack along with some optimizations like KoreK attacks, as well as the all-new PTW attack, thus making the attack' and is a popular penetration testing tool in the network & admin category. There are four alternatives to Aircrack-ng for Linux. The best Aircrack-ng alternative is Wifite, which is both free and Open Source. Other great apps like Aircrack-ng are reaver, Fern Wifi Cracker and netsniff-ng.