diff --git a/src/sweets/download.py b/src/sweets/download.py
index 80d32d1..74c1cf5 100644
--- a/src/sweets/download.py
+++ b/src/sweets/download.py
@@ -25,6 +25,7 @@
 import zipfile
 from concurrent.futures import ThreadPoolExecutor
 from datetime import date, datetime
+from enum import Enum
 from functools import lru_cache
 from pathlib import Path
 from typing import Any, Optional
@@ -45,6 +46,11 @@
 DIRNAME = os.path.dirname(os.path.abspath(__file__))
 
 
+class FlightDirection(str, Enum):
+    ASCENDING = "ASCENDING"
+    DESCENDING = "DESCENDING"
+
+
 class ASFQuery(YamlModel):
     """Class holding the Sentinel-1 ASF query parameters."""
 
@@ -83,11 +89,10 @@ class ASFQuery(YamlModel):
         alias="relativeOrbit",
         description="Path number",
     )
-    flight_direction: Optional[str] = Field(
+    flight_direction: Optional[FlightDirection] = Field(
         None,
         alias="flightDirection",
-        choices=["ASCENDING", "DESCENDING"],
-        description="Ascending or descending",
+        description="Direction of satellite during acquisition.",
     )
     frames: Optional[tuple[int, int]] = Field(
         None,