diff --git a/sw/tools/Makefile b/sw/tools/Makefile
index d7ae73bd2c..cb36737d1e 100644
--- a/sw/tools/Makefile
+++ b/sw/tools/Makefile
@@ -40,7 +40,7 @@ gen_flight_plan.out : $(FP_CMO) ../lib/ocaml/lib-pprz.cma
 	$(Q)$(OCAMLC) $(INCLUDES) -custom -o $@ unix.cma str.cma xml-light.cma ivy-ocaml.cma lib-pprz.cma $^
 
 fp_parser.cmo : fp_parser.cmi fp_syntax.cmi
-fp_proc.cmo : fp_parser.cmi
+fp_proc.cmo : fp_parser.cmi fp_proc.cmi
 fp_parser.cmi : fp_parser.ml fp_syntax.cmi
 fp_lexer.cmi : fp_syntax.cmi
 fp_lexer.cmo : fp_lexer.cmi
diff --git a/sw/tools/fp_proc.mli b/sw/tools/fp_proc.mli
new file mode 100644
index 0000000000..59224ecf1f
--- /dev/null
+++ b/sw/tools/fp_proc.mli
@@ -0,0 +1,37 @@
+(*
+ * $Id$
+ *
+ * Flight plan preprocessing (from XML to XML)
+ *  
+ * Copyright (C) 2009 ENAC, Pascal Brisset, Antoine Drouin
+ *
+ * This file is part of paparazzi.
+ *
+ * paparazzi is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * paparazzi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with paparazzi; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA. 
+ *
+ *)
+
+val parse_expression : string -> Fp_syntax.expression
+
+val process_paths : Xml.xml -> Xml.xml
+(** [process_paths flight_plan] *)
+
+val process_relative_waypoints : Xml.xml -> Xml.xml
+(** [process_relative_waypoints flight_plan] Handles the [wp_qdr, wp_dist]
+    and [from_qdr, from_dist] by generating new waypoints *)
+
+val process_includes : string -> Xml.xml -> Xml.xml
+(** [process_includes directory file_name] *)