diff --git a/sw/ground_segment/cockpit/live.ml b/sw/ground_segment/cockpit/live.ml
index 7787fa11aa..540a5500a0 100644
--- a/sw/ground_segment/cockpit/live.ml
+++ b/sw/ground_segment/cockpit/live.ml
@@ -102,7 +102,7 @@ type aircraft = {
   mutable ground_prox : bool;
   mutable got_track_status_timer : int;
   mutable last_dist_to_wp : float;
-  mutable dl_values : float array;
+  mutable dl_values : string option array;
   mutable last_unix_time : float;
   mutable airspeed : float
 }
@@ -739,8 +739,8 @@ let create_ac = fun alert (geomap:G.widget) (acs_notebook:GPack.notebook) (ac_id
               let id = settings_tab#assoc "snav_desired_tow" in
               let set_appointment = fun _ ->
                 begin try
-                        let v = ac.dl_values.(id) in
-                        let t = Unix.gmtime (Latlong.unix_time_of_tow (truncate v)) in
+                        let v = match ac.dl_values.(id) with None -> raise Not_found | Some x -> int_of_string x in
+                        let t = Unix.gmtime (Latlong.unix_time_of_tow v) in
                         ac.strip#set_label "apt" (sprintf "%d:%02d:%02d" t.Unix.tm_hour t.Unix.tm_min t.Unix.tm_sec)
                   with _ -> () end;
                 true
@@ -910,10 +910,13 @@ let listen_dl_value = fun () ->
     match ac.dl_settings_page with
         Some settings ->
           let csv = Pprz.string_assoc "values" vs in
-          let values = Array.map float_of_string (Array.of_list (Str.split list_separator csv)) in
+          let string_value = fun v -> match v with "?" -> None | _ -> Some v in
+          let values = Array.map string_value (Array.of_list (Str.split list_separator csv)) in
           ac.dl_values <- values;
           for i = 0 to min (Array.length values) settings#length - 1 do
-            settings#set i (try values.(i) with _ -> failwith (sprintf "values.(%d)" i))
+            try
+              settings#set i values.(i)
+            with _ -> ()
           done
       | None -> () in
   safe_bind "DL_VALUES" get_dl_value
diff --git a/sw/ground_segment/cockpit/live.mli b/sw/ground_segment/cockpit/live.mli
index 53ed41711e..4222af0202 100644
--- a/sw/ground_segment/cockpit/live.mli
+++ b/sw/ground_segment/cockpit/live.mli
@@ -59,7 +59,7 @@ type aircraft = private {
     mutable ground_prox : bool;
     mutable got_track_status_timer : int;
     mutable last_dist_to_wp : float;
-    mutable dl_values : float array;
+    mutable dl_values : string option array;
     mutable last_unix_time : float;
     mutable airspeed : float
   }
diff --git a/sw/ground_segment/cockpit/page_settings.ml b/sw/ground_segment/cockpit/page_settings.ml
index 4080915016..0dd1b0ef3f 100644
--- a/sw/ground_segment/cockpit/page_settings.ml
+++ b/sw/ground_segment/cockpit/page_settings.ml
@@ -31,15 +31,26 @@ class setting = fun (i:int) (xml:Xml.xml) (current_value:GMisc.label) set_defaul
 object
   method index = i
   method xml = xml
+  val mutable last_known_value = None
+  method last_known_value =
+    match last_known_value with None -> raise Not_found | Some v -> v
   method current_value =
     let auc = Pprz.alt_unit_coef_of_xml xml in
     let (alt_a, alt_b) = Ocaml_tools.affine_transform auc in
     (float_of_string current_value#text -. alt_b) /. alt_a
   method update = fun s ->
-    if current_value#text <> s then begin
-      current_value#set_text s;
-      try set_default (float_of_string s) with Failure "float_of_string" -> ()
-    end
+    (* if not yet confirmed, display "?" *)
+    if s = "?" then
+      current_value#set_text "?"
+    else
+      if current_value#text <> s then begin
+        current_value#set_text s;
+        try
+          let v = float_of_string s in
+          last_known_value <- Some v;
+          set_default v
+        with Failure "float_of_string" -> ()
+      end
 end
 
 let pipe_regexp = Str.regexp "|"
@@ -183,9 +194,11 @@ let one_setting = fun (i:int) (do_change:int -> float -> unit) packing dl_settin
   let set_default = fun x ->
     if not !modified then set_default x else () in
 
-  (* Update value *)
+  (* click current_value lable to request an update *)
   let callback = fun _ ->
-    do_change i infinity; true in
+    do_change i infinity;
+    current_value#set_text "?";
+    true in
   ignore (eb#event#connect#button_press ~callback);
 
   (* Auto check button *)
@@ -199,10 +212,12 @@ let one_setting = fun (i:int) (do_change:int -> float -> unit) packing dl_settin
   let _icon = GMisc.image ~stock:`APPLY ~packing:commit_but#add () in
   let callback = fun x ->
     prev_value := (try Some ((float_of_string current_value#text-.alt_b)/.alt_a) with _ -> None);
-    commit x
+    commit x;
+    current_value#set_text "?"
   in
   ignore (commit_but#connect#clicked ~callback);
   tooltips#set_tip commit_but#coerce ~text:"Commit";
+  tooltips#set_tip current_value#coerce ~text:"Current value, click to request update.";
 
   (* Undo button *)
   let undo_but = GButton.button ~packing:hbox#pack () in
@@ -309,26 +324,31 @@ object (self)
   method widget = sw#coerce
   method length = length
   method keys = !keys
-  method set = fun i v ->
+  method set = fun i value ->
     if visible self#widget then
       let setting = variables.(i) in
-      let auc = Pprz.alt_unit_coef_of_xml setting#xml in
-      let (alt_a, alt_b) = Ocaml_tools.affine_transform auc in
-      let v = alt_a *. v +. alt_b in
-      let s = string_of_float v in
+      let s, v = match value with
+        | None -> "?", -1
+        | Some x ->
+          let v = try float_of_string x with _ -> failwith (sprintf "Pages.settings#set:wrong values.(%d) = %s" i x) in
+          let auc = Pprz.alt_unit_coef_of_xml setting#xml in
+          let (alt_a, alt_b) = Ocaml_tools.affine_transform auc in
+          let v = alt_a *. v +. alt_b in
+          string_of_float v, truncate v
+      in
       if i < 0 || i >= Array.length variables then
         failwith (sprintf "Pages.settings#set: %d out of bounnds (length=%d)" i (Array.length variables));
       let s =
         let values = values_of_dl_setting setting#xml in
         try
           let lower = int_of_string (ExtXml.attrib setting#xml "min") in
-          values.(truncate v - lower)
+          values.(v - lower)
         with
             _ -> s in
       setting#update s
   method assoc var = List.assoc var assocs
   method save = fun airframe_filename ->
-    let settings = Array.fold_right (fun setting r -> try (setting#index, setting#xml, setting#current_value)::r with _ -> r) variables [] in
+    let settings = Array.fold_right (fun setting r -> try (setting#index, setting#xml, setting#last_known_value)::r with _ -> r) variables [] in
     SaveSettings.popup airframe_filename (Array.of_list settings) do_change
 end
 
diff --git a/sw/ground_segment/cockpit/page_settings.mli b/sw/ground_segment/cockpit/page_settings.mli
index 52691f6a67..73b1600ba5 100644
--- a/sw/ground_segment/cockpit/page_settings.mli
+++ b/sw/ground_segment/cockpit/page_settings.mli
@@ -26,7 +26,7 @@
 class settings : ?visible:(GObj.widget -> bool) -> Xml.xml list -> (int -> float -> unit) -> (string -> GObj.widget -> unit) ->
   object
     method length : int (** Total number of settings *)
-    method set : int -> float -> unit (** Set the current value *)
+    method set : int -> string option -> unit (** Set the current value *)
     method assoc : string -> int
     method widget : GObj.widget
     method save : string -> unit
diff --git a/sw/ground_segment/tmtc/aircraft.ml b/sw/ground_segment/tmtc/aircraft.ml
index 2d854e2992..383478880d 100644
--- a/sw/ground_segment/tmtc/aircraft.ml
+++ b/sw/ground_segment/tmtc/aircraft.ml
@@ -184,7 +184,7 @@ type aircraft = {
   mutable stage_time : int;
   mutable block_time : int;
   mutable horiz_mode : horiz_mode;
-  dl_setting_values : float array;
+  dl_setting_values : float option array;
   mutable nb_dl_setting_values : int;
   mutable survey : (Latlong.geographic * Latlong.geographic) option;
   datalink_status : datalink_status;
@@ -217,7 +217,7 @@ let new_aircraft = fun id name fp airframe ->
     cam = { phi = 0.; theta = 0. ; target=(0.,0.)};
     fbw = { rc_status = "???"; rc_mode = "???"; rc_rate=0; pprz_mode_msgs_since_last_fbw_status_msg=0 };
     svinfo = svsinfo_init;
-    dl_setting_values = Array.create max_nb_dl_setting_values 42.;
+    dl_setting_values = Array.create max_nb_dl_setting_values None;
     nb_dl_setting_values = 0;
     horiz_mode = UnknownHorizMode;
     horizontal_mode = 0;
diff --git a/sw/ground_segment/tmtc/aircraft.mli b/sw/ground_segment/tmtc/aircraft.mli
index bda45823c1..67a0a0890d 100644
--- a/sw/ground_segment/tmtc/aircraft.mli
+++ b/sw/ground_segment/tmtc/aircraft.mli
@@ -136,7 +136,7 @@ type aircraft = {
     mutable stage_time : int;
     mutable block_time : int;
     mutable horiz_mode : horiz_mode;
-    dl_setting_values : float array;
+    dl_setting_values : float option array;
     mutable nb_dl_setting_values : int;
     mutable survey : (Latlong.geographic * Latlong.geographic) option;
     datalink_status : datalink_status;
diff --git a/sw/ground_segment/tmtc/fw_server.ml b/sw/ground_segment/tmtc/fw_server.ml
index ac639a5b7e..756acea4bb 100644
--- a/sw/ground_segment/tmtc/fw_server.ml
+++ b/sw/ground_segment/tmtc/fw_server.ml
@@ -298,7 +298,7 @@ let log_and_parse = fun ac_name (a:Aircraft.aircraft) msg values ->
     | "DL_VALUE" ->
       let i = ivalue "index" in
       if i < max_nb_dl_setting_values then begin
-        a.dl_setting_values.(i) <- fvalue "value";
+        a.dl_setting_values.(i) <- Some (fvalue "value");
         a.nb_dl_setting_values <- max a.nb_dl_setting_values (i+1)
       end else
         failwith "Too much dl_setting values !!!"
diff --git a/sw/ground_segment/tmtc/server.ml b/sw/ground_segment/tmtc/server.ml
index a184cc612e..5cdd15f4cd 100644
--- a/sw/ground_segment/tmtc/server.ml
+++ b/sw/ground_segment/tmtc/server.ml
@@ -199,7 +199,9 @@ let send_dl_values = fun a ->
   if a.nb_dl_setting_values > 0 then
     let csv = ref "" in
     for i = 0 to a.nb_dl_setting_values - 1 do
-      csv := sprintf "%s%f," !csv a.dl_setting_values.(i)
+      match a.dl_setting_values.(i) with
+      | None -> csv := sprintf "%s?," !csv
+      | Some s -> csv := sprintf "%s%f," !csv s
     done;
     let vs = ["ac_id", Pprz.String a.id; "values", Pprz.String !csv] in
     Ground_Pprz.message_send my_id "DL_VALUES" vs
@@ -677,7 +679,11 @@ let setting = fun logging _sender vs ->
              "ac_id", Pprz.String ac_id;
              "value", List.assoc "value" vs] in
   Dl_Pprz.message_send dl_id "SETTING" vs;
-  log logging ac_id "SETTING" vs
+  log logging ac_id "SETTING" vs;
+  (* mark the setting as not yet confirmed *)
+  let ac = Hashtbl.find aircrafts ac_id in
+  let idx = Pprz.int_of_value (List.assoc "index" vs) in
+  ac.dl_setting_values.(idx) <- None
 
 
 (** Got a GET_DL_SETTING, and send an GET_SETTING *)
@@ -686,7 +692,11 @@ let get_setting = fun logging _sender vs ->
   let vs = [ "index", List.assoc "index" vs;
              "ac_id", Pprz.String ac_id ] in
   Dl_Pprz.message_send dl_id "GET_SETTING" vs;
-  log logging ac_id "GET_SETTING" vs
+  log logging ac_id "GET_SETTING" vs;
+  (* mark the setting as not yet confirmed *)
+  let ac = Hashtbl.find aircrafts ac_id in
+  let idx = Pprz.int_of_value (List.assoc "index" vs) in
+  ac.dl_setting_values.(idx) <- None
 
 
 (** Got a JUMP_TO_BLOCK, and send an BLOCK *)
diff --git a/sw/ground_segment/tmtc/settings.ml b/sw/ground_segment/tmtc/settings.ml
index e8ae766efd..0569ccc69c 100644
--- a/sw/ground_segment/tmtc/settings.ml
+++ b/sw/ground_segment/tmtc/settings.ml
@@ -59,7 +59,7 @@ let one_ac = fun (notebook:GPack.notebook) ac_name ->
 
     (* Bind to values updates *)
     let get_dl_value = fun _sender vs ->
-      settings#set (Pprz.int_assoc "index" vs) (Pprz.float_assoc "value" vs)
+      settings#set (Pprz.int_assoc "index" vs) (Some (string_of_float (Pprz.float_assoc "value" vs)))
     in
     ignore (Tele_Pprz.message_bind "DL_VALUE" get_dl_value);