If you installed Back Track 2 into your hdd and if you want to update the aircrack-ng suite, here’s the commands to do so.
Download the source here.
tar -zxvf aircrack-ng-0.9.1.tar.gz
make -B install
make install will throw out some errors, so just do it with a “-B”
-B, –always-make Unconditionally make all targets.