diff --git a/sw/tools/gen_flight_plan.ml b/sw/tools/gen_flight_plan.ml
index 6788e0a8ce..899239b29a 100644
--- a/sw/tools/gen_flight_plan.ml
+++ b/sw/tools/gen_flight_plan.ml
@@ -557,7 +557,7 @@ let check_geo_ref = fun xml ->
   let max_d = min 1000. (get_float "max_dist_from_home") in
   let check_zone = fun u ->
     if (utm_of WGS84 (of_utm WGS84 u)).utm_zone <> utm0.utm_zone then
-      failwith "Fatal error: You are too close (less than twice the max distance) to an UTM zone border !" in
+      prerr_endline "Warning: You are close (less than twice the max distance) to an UTM zone border ! The navigation will not work unless the GPS_USE_LATLONG flag is set and the GPS receiver configured to send the POSLLH message." in
   check_zone { utm0 with utm_x = utm0.utm_x +. 2.*.max_d };
   check_zone { utm0 with utm_x = utm0.utm_x -. 2.*.max_d };
 
@@ -642,9 +642,10 @@ let () =
   let xml_file = ref "fligh_plan.xml"
   and dump = ref false
   and gen_sectors = ref false in
-  Arg.parse [("-dump", Arg.Set dump, "Dump compile result");
+  Arg.parse [("-check", Arg.Set check_expressions, "Enable expression checking");
+	     ("-dump", Arg.Set dump, "Dump compile result");
 	     ("-sectors", Arg.Set gen_sectors, "Generatess inside functions for sectors.xml");
-	     ("-check", Arg.Set check_expressions, "Enable expression checking")]
+	     ]
     (fun f -> xml_file := f)
     "Usage:";
   if !xml_file = "" then