airbase-ng: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/airbase-ng - from package: aircrack-ng

You may install the required package with command apt-get install {package}

Error in other languages:
airbase-ng: bevel nie gevind nie
airbase-ng: comandă negăsită
airbase-ng: comando não encontrado
airbase-ng: commande introuvable
airbase-ng: command not found
airbase-ng: käsku ei ole
airbase-ng: không tìm thấy lệnh
airbase-ng: komanda nerasta
airbase-ng: Kommando nicht gefunden.
airbase-ng: kommandot finns inte
airbase-ng: komut yok
airbase-ng: nie znaleziono polecenia
airbase-ng: níor aimsíodh an t-ordú
airbase-ng: no se encontró la orden
airbase-ng: no s'ha trobat l'ordre
airbase-ng: opdracht niet gevonden
airbase-ng: parancs nem található
airbase-ng: perintah tidak ditemukan
airbase-ng: príkaz nenájdený
airbase-ng: příkaz nenalezen
airbase-ng: команда не найдена
airbase-ng: командата не е открита
airbase-ng: 命令找不到
airbase-ng: コマンドが見つかりません