Short-listed candidates are subject to formal tests on essential and/or desirable proficiencies in NATO's official languages i.e. English and French (only in non mother tongue).
Description of Standard Language Proficiency
Level 1 - Elementary
Level 2 - Fair (limited working)
Level 3 - Good (minimum professional)
Level 4 - Very good (full professional)
Level 5 - Excellent (native speaker/bilingual)