diff --git a/AircraftSchedule.proto b/AircraftSchedule.proto
index d46bb92..9857ccb 100644
--- a/AircraftSchedule.proto
+++ b/AircraftSchedule.proto
@@ -5,8 +5,9 @@ import "Aircraft.proto";
 import "BaseTypes.proto";
 
 message AircraftSchedule {
-    Aircraft aircraft           = 1; // aircraft information
-    string arrivalRoute         = 2; // planned arrival route
-    string arrivalRunway        = 3; // planned arrival runway
-    repeated Waypoint waypoints = 4; // contains the planned waypoints with the PTA
+    string callsign             = 1; // aircraft's callsign
+    bool fixed                  = 2; // indicates if the sequence is fixed
+    string arrivalRoute         = 3; // planned arrival route
+    string arrivalRunway        = 4; // planned arrival runway
+    repeated Waypoint waypoints = 5; // contains the planned waypoints with the PTA
 }