diff --git a/src/MNH/aircraft_balloon.f90 b/src/MNH/aircraft_balloon.f90
index 7538a4068d1190fd4ac90017ab86906e4d763ef2..4dd66cddee69fafebae5bd2bff7b287e87ee57e3 100644
--- a/src/MNH/aircraft_balloon.f90
+++ b/src/MNH/aircraft_balloon.f90
@@ -34,7 +34,7 @@ REAL, DIMENSION(:,:),     INTENT(IN)     :: PTS    ! surface temperature
 ! ++ OC
 REAL, DIMENSION(:,:,:),   INTENT(IN)     :: PRHODREF ! dry air density of the reference state
 REAL, DIMENSION(:,:,:),   INTENT(IN)     :: PCIT     ! pristine ice concentration
-REAL, DIMENSION(:,:),INTENT(IN) :: PSEA
+REAL, DIMENSION(:,:),OPTIONAL,INTENT(IN) :: PSEA
 ! -- OC
 !
 !-------------------------------------------------------------------------------
diff --git a/src/MNH/aircraft_balloon_evol.f90 b/src/MNH/aircraft_balloon_evol.f90
index 719d5de2fffe1382bed7076004e02be4d39dd69b..0ac512afb23da5dc3a8aad719a348aa58e00cac1 100644
--- a/src/MNH/aircraft_balloon_evol.f90
+++ b/src/MNH/aircraft_balloon_evol.f90
@@ -37,7 +37,7 @@ REAL, DIMENSION(:,:,:),   INTENT(IN)     :: PRHODREF ! dry air density of the re
 REAL, DIMENSION(:,:,:),   INTENT(IN)     :: PCIT     ! pristine ice concentration
 !
 CLASS(TFLYERDATA),        INTENT(INOUT)  :: TPFLYER! balloon/aircraft
-REAL, DIMENSION(:,:),     INTENT(IN)     :: PSEA
+REAL, DIMENSION(:,:), OPTIONAL, INTENT(IN) :: PSEA
 !
 !-------------------------------------------------------------------------------
 !
diff --git a/src/MNH/modeln.f90 b/src/MNH/modeln.f90
index 2582fea44960ab4ce0e50f3d90d84f08a16afc23..01be406455d0fdb730ddb1beb61930d4eae62f3a 100644
--- a/src/MNH/modeln.f90
+++ b/src/MNH/modeln.f90
@@ -2104,12 +2104,23 @@ XT_STEP_SWA = XT_STEP_SWA + ZTIME2 - ZTIME1 - XTIME_BU_PROCESS
 !
 ZTIME1 = ZTIME2
 !
-IF (LFLYER)                                                                   &
-  CALL AIRCRAFT_BALLOON(XTSTEP,                                               &
+IF (LFLYER) THEN
+  IF (CSURF=='EXTE') THEN
+    ALLOCATE(ZSEA(IIU,IJU))
+    ZSEA(:,:) = 0.
+    CALL MNHGET_SURF_PARAM_n (PSEA=ZSEA(:,:))
+    CALL AIRCRAFT_BALLOON(XTSTEP,                                             &
                       XXHAT, XYHAT, XZZ, XMAP, XLONORI, XLATORI,              &
                       XUT, XVT, XWT, XPABST, XTHT, XRT, XSVT, XTKET, XTSRAD,  &
                       XRHODREF,XCIT,PSEA=ZSEA(:,:))
-
+    DEALLOCATE(ZSEA)
+  ELSE
+    CALL AIRCRAFT_BALLOON(XTSTEP,                                             &
+                      XXHAT, XYHAT, XZZ, XMAP, XLONORI, XLATORI,              &
+                      XUT, XVT, XWT, XPABST, XTHT, XRT, XSVT, XTKET, XTSRAD,  &
+                      XRHODREF,XCIT)
+  END IF
+END IF
 
 !-------------------------------------------------------------------------------
 !