diff --git a/definitions/mars/class.table b/definitions/mars/class.table
index f2338f0ad..efe2be6b1 100644
--- a/definitions/mars/class.table
+++ b/definitions/mars/class.table
@@ -49,6 +49,7 @@
 48 eh C3S European hydrology
 49 gh C3S Global hydrology
 50 ci CERISE project
+51 ai Operational AIFS
 99 te Test
 100 at Austria
 101 be Belgium