diff --git a/src/MNH/aircraft_balloon_evol.f90 b/src/MNH/aircraft_balloon_evol.f90
index 6d2f5a80b151281b25a24038bb0ab8632fcd5d0d..dcbdd6349d012cb4ceea2734c75146d1c55a5c4b 100644
--- a/src/MNH/aircraft_balloon_evol.f90
+++ b/src/MNH/aircraft_balloon_evol.f90
@@ -326,6 +326,7 @@ SELECT TYPE ( TPFLYER )
     END IF
 
     ! In flight
+    ! The condition "ABS( TPFLYER%TPOS_CUR - TDTCUR ) < XTIMETHRESH" is necessary if the balloon changes of model
     INFLIGHTONMODEL: IF ( TPFLYER%LFLY .AND. .NOT. TPFLYER%LCRASH .AND. TPFLYER%NMODEL == IMI &
                           .AND. ABS( TPFLYER%TPOS_CUR - TDTCUR ) < XTIMETHRESH ) THEN
       ISOWNERBAL: IF ( TPFLYER%NRANK_CUR == ISP ) THEN