diff --git a/skais/ais/ais_trajectory.py b/skais/ais/ais_trajectory.py
index 69c96979b866b759b1d673317d101cdbc2231359..39a5ad5b08f179d144e94508fc0f4c1e8f88e8e1 100644
--- a/skais/ais/ais_trajectory.py
+++ b/skais/ais/ais_trajectory.py
@@ -51,7 +51,7 @@ def apply_time_sequence(dat, time, func):
 class AISTrajectory(AISPoints):
     def __init__(self, df, interpolation_time=None):
         df = df.drop_duplicates(subset=['ts_sec'])
-
+        df = df.sort_values(by=['ts_sec'])
         if interpolation_time and len(df.index) > 4:
 
             float_columns = ['longitude', 'latitude', 'cog', 'heading', 'rot', 'sog', 'diff']