diff --git a/Makefile b/Makefile
index f2b56eb455..da3e25973d 100644
--- a/Makefile
+++ b/Makefile
@@ -78,6 +78,9 @@ fbw fly_by_wire: ac_h
 ap autopilot: ac_h
 	cd $(AIRBORNE); $(MAKE) TARGET=ap all
 
+sim: ac_h
+	cd $(AIRBORNE); $(MAKE) TARGET=sim ARCHI=sim all
+
 upload_fbw: fbw
 	cd $(AIRBORNE); $(MAKE) TARGET=fbw upload
 
diff --git a/conf/messages.xml b/conf/messages.xml
index 4ff949160e..a5859f1459 100644
--- a/conf/messages.xml
+++ b/conf/messages.xml
@@ -66,7 +66,7 @@
   </message>
 
   <message name="PPRZ_MODE" ID="11" period="5" >
-    <field name="ap_mode" type="uint8" values="MANUAL|AUTO1|AUTO2|HOME|FAILSAFE"/>
+    <field name="ap_mode" type="uint8" values="MANUAL|AUTO1|AUTO2|HOME|NOGPS|FAILSAFE"/>
     <field name="ap_gaz" type="uint8" values="MANUAL|AUTO_GAZ|AUTO_CLIMB|AUTO_ALT"/>
     <field name="ap_lateral" type="uint8" values="MANUAL|ROLL_RATE|ROLL|COURSE"/>
     <field name="ap_horizontal" type="uint8" values="WAYPOINT|ROUTE|CIRCLE"/>
diff --git a/sw/airborne/autopilot.h b/sw/airborne/autopilot.h
index f88826604e..5ae8f77b26 100644
--- a/sw/airborne/autopilot.h
+++ b/sw/airborne/autopilot.h
@@ -92,7 +92,6 @@ extern bool_t rc_event_1, rc_event_2;
 extern float slider_1_val, slider_2_val;
 
 extern bool_t launch;
-extern uint16_t cputime; /**  in seconds */
 
 
 #define ModeUpdate(_mode, _value) { \
diff --git a/sw/airborne/infrared.c b/sw/airborne/infrared.c
index 7e72ad5e6c..c042e96a5e 100644
--- a/sw/airborne/infrared.c
+++ b/sw/airborne/infrared.c
@@ -33,6 +33,7 @@
 #include "autopilot.h"
 #include "estimator.h"
 #include "downlink.h"
+#include "sys_time.h"
 
 int16_t ir_roll;
 int16_t ir_pitch;
@@ -125,7 +126,7 @@ uint8_t calib_status = NO_CALIB;
 void ground_calibrate( bool_t triggered ) {
   switch (calib_status) {
   case NO_CALIB:
-    if (cputime < MAX_DELAY_FOR_CALIBRATION && pprz_mode == PPRZ_MODE_AUTO1 ) {
+    if (cpu_time < MAX_DELAY_FOR_CALIBRATION && pprz_mode == PPRZ_MODE_AUTO1 ) {
       calib_status = WAITING_CALIB_CONTRAST;
       DOWNLINK_SEND_CALIB_START();
     }
diff --git a/sw/airborne/main_ap.c b/sw/airborne/main_ap.c
index 975cb3e73b..c003f86c50 100644
--- a/sw/airborne/main_ap.c
+++ b/sw/airborne/main_ap.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *  
- * Copyright (C) 2003-2005  Pascal Brisset, Antoine Drouin
+ * Copyright (C) 2003-2005  Antoine Drouin
  *
  * This file is part of paparazzi.
  *
@@ -21,10 +21,6 @@
  * Boston, MA 02111-1307, USA. 
  *
  */
-/** \file main.c
- *  \brief Regroup main functions
- *
- */
 
 #include <math.h>
 
@@ -40,6 +36,7 @@
 #include "cam.h"
 #include "traffic_info.h"
 #include "link_mcu.h"
+#include "sys_time.h"
 
 #ifdef LED
 #include "led.h"
@@ -65,10 +62,6 @@
 uint8_t  inflight_calib_mode = IF_CALIB_MODE_NONE;
 
 
-//
-//
-// FIXME estimator_flight_time should not be manipuled here anymore
-//
 /** Define minimal speed for takeoff in m/s */
 #define MIN_SPEED_FOR_TAKEOFF 5.
 
@@ -76,9 +69,6 @@ uint8_t  inflight_calib_mode = IF_CALIB_MODE_NONE;
 uint8_t fatal_error_nb = 0;
 static const uint16_t version = 1;
 
-/**  in seconds */
-uint16_t cputime = 0;
-
 uint8_t pprz_mode = PPRZ_MODE_MANUAL;
 uint8_t vertical_mode = VERTICAL_MODE_MANUAL;
 uint8_t lateral_mode = LATERAL_MODE_MANUAL;
@@ -115,8 +105,8 @@ float energy; /** Fuel consumption */
 static inline uint8_t pprz_mode_update( void ) {
   /** We remain in home mode until explicit reset from the RC */
   if ((pprz_mode != PPRZ_MODE_HOME &&
-				pprz_mode != PPRZ_MODE_GPS_OUT_OF_ORDER)
-				|| CheckEvent(rc_event_1)) {
+       pprz_mode != PPRZ_MODE_GPS_OUT_OF_ORDER)
+      || CheckEvent(rc_event_1)) {
     ModeUpdate(pprz_mode, PPRZ_MODE_OF_PULSE(from_fbw.channels[RADIO_MODE], from_fbw.status));
   } else
     return FALSE;
@@ -299,7 +289,7 @@ static void navigation_task( void ) {
 	
   /** Test if we lost the GPS */
   if (!GPS_FIX_VALID(gps_mode) ||
-      (cputime - last_gps_msg_t > FAILSAFE_DELAY_WITHOUT_GPS)) {
+      (cpu_time - last_gps_msg_t > FAILSAFE_DELAY_WITHOUT_GPS)) {
     /** If aircraft is launch and is in autonomus mode, go into
 	PPRZ_MODE_GPS_OUT_OF_ORDER mode (Failsafe). */
     if (launch && (pprz_mode == PPRZ_MODE_AUTO2 ||
@@ -398,7 +388,7 @@ inline void periodic_task( void ) {
   }
   if (!_1Hz) {
     if (estimator_flight_time) estimator_flight_time++;
-    cputime++;
+    cpu_time++;
     stage_time_ds = (int16_t)(stage_time_ds+.5);
     stage_time++;
     block_time++;
@@ -431,7 +421,7 @@ inline void periodic_task( void ) {
 	estimator_hspeed_mod > MIN_SPEED_FOR_TAKEOFF) {
       estimator_flight_time = 1;
       launch = TRUE; /* Not set in non auto launch */
-      DOWNLINK_SEND_TAKEOFF(&cputime);
+      DOWNLINK_SEND_TAKEOFF(&cpu_time);
     }
     break;
     /*  default: */
diff --git a/sw/ground_segment/tmtc/server.ml b/sw/ground_segment/tmtc/server.ml
index 383ac97ec6..c8ae32ddb1 100644
--- a/sw/ground_segment/tmtc/server.ml
+++ b/sw/ground_segment/tmtc/server.ml
@@ -52,7 +52,7 @@ let rec norm_course =
     else c
 
 (** FIXME: Should be read from messages.xml *)
-let ap_modes = [|"MANUAL";"AUTO1";"AUTO2";"HOME"|]
+let ap_modes = [|"MANUAL";"AUTO1";"AUTO2";"HOME";"NOGPS"|]
 let gaz_modes = [|"MANUAL";"GAZ";"CLIMB";"ALT"|]
 let lat_modes = [|"MANUAL";"ROLL_RATE";"ROLL";"COURSE"|]
 let gps_modes = [|"NOFIX";"DRO";"2D";"3D";"GPSDRO"|]
diff --git a/sw/simulator/Makefile b/sw/simulator/Makefile
index be7b1d1d41..3fa71db10c 100644
--- a/sw/simulator/Makefile
+++ b/sw/simulator/Makefile
@@ -32,7 +32,7 @@ SIMHCMO=$(SIMHML:%.ml=%.cmo)
 SIMSML = stdlib.ml data.ml flightModel.ml gps.ml sitl.ml sim.ml
 SIMSCMO=$(SIMSML:%.ml=%.cmo)
 SIMSCMX=$(SIMSML:%.ml=%.cmx)
-SIMSC = sim_ir.c sim_gps.c sim_ap.c estimator.c infrared.c gps.c pid.c nav.c main_ap.c cam.c traffic_info.c
+SIMSC = sim_ir.c sim_gps.c sim_ap.c sys_time.c estimator.c infrared.c gps.c pid.c nav.c main_ap.c cam.c traffic_info.c
 SIMSO=$(SIMSC:%.c=$(OBJDIR)/%.o)
 SIMSA=sims.cma
 
diff --git a/sw/simulator/sys_time_hw.h b/sw/simulator/sys_time_hw.h
new file mode 100644
index 0000000000..e69de29bb2