diff --git a/src/legs.rs b/src/legs.rs
index 6779fb4..3aff684 100644
--- a/src/legs.rs
+++ b/src/legs.rs
@@ -51,7 +51,7 @@ fn landed(prev_position: &Position, position: &Position) -> bool {
         (&prev_position, &position),
         (Position::Flying { .. }, Position::Flying { .. })
     ) && position.datetime() - prev_position.datetime() > time::Duration::minutes(5)
-        && position.altitude() < 10000.0)
+        && (position.altitude() < 10000.0 || prev_position.altitude() < 10000.0))
 }
 
 fn is_grounded(prev_position: &Position, position: &Position) -> bool {
@@ -62,7 +62,7 @@ fn is_grounded(prev_position: &Position, position: &Position) -> bool {
         (&prev_position, &position),
         (Position::Flying { .. }, Position::Flying { .. })
     ) && position.datetime() - prev_position.datetime() > time::Duration::minutes(5)
-        && position.altitude() < 10000.0)
+        && (position.altitude() < 10000.0 || prev_position.altitude() < 10000.0))
 }
 
 /// Returns a set of [`Leg`]s from a sequence of [`Position`]s.
diff --git a/tests/it/main.rs b/tests/it/main.rs
index c6a9b4d..eb548cf 100644
--- a/tests/it/main.rs
+++ b/tests/it/main.rs
@@ -96,3 +96,10 @@ async fn multi_day_legs() -> Result<(), Box<dyn Error>> {
     assert_eq!(legs.len(), 6);
     Ok(())
 }
+
+#[tokio::test]
+async fn case_459257_2023_12_17() -> Result<(), Box<dyn Error>> {
+    let legs = legs(date!(2023 - 12 - 17), date!(2023 - 12 - 20), "459257", None).await?;
+    assert_eq!(legs.len(), 4);
+    Ok(())
+}