diff --git a/nav.py b/nav.py
index 35ff6e0..ed6e4c9 100644
--- a/nav.py
+++ b/nav.py
@@ -2,6 +2,7 @@
 """Navigation computer of the SS Probably Fine.
 
 Usage: python3 nav.py DESTINATION
+       python3 nav.py --list
 """
 
 import sys
@@ -64,6 +65,10 @@ def plan(destination):
 
 
 def main():
+    if sys.argv[1] == "--list":
+        for key in sorted(ROUTES):
+            print(f"{key:12} {NAMES[key]}")
+        return
     destination = sys.argv[1]
     if destination not in ROUTES:
         known = ", ".join(sorted(ROUTES))