airrac: 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 CentOS possible default full paths are:

/usr/bin/airrac - from package: airrac

You may install the required package with command yum install {package}

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