airport-hostmon: 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/bin/airport-hostmon - from package: airport-utils

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

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