diff --git a/config-merger/script/merge_config.py b/config-merger/script/merge_config.py
index 8c1c07d..3ae2f7a 100755
--- a/config-merger/script/merge_config.py
+++ b/config-merger/script/merge_config.py
@@ -132,7 +132,12 @@ def generate_env_file(config, output_dir):
     adsblol = bool(tar1090_config.get('adsblol_fallback', False)) and sited
     lines.append("# adsb.lol integration\n")
     lines.append(f"ADSBLOL_ENABLED={'true' if adsblol else 'false'}\n")
-    lines.append(f"ADSBLOL_RADIUS={tar1090_config.get('adsblol_radius', 40)}\n\n")
+    lines.append(f"ADSBLOL_RADIUS={tar1090_config.get('adsblol_radius', 40)}\n")
+    # Ordered chain of sources the tar1090 proxy tries until one answers.
+    # Written even when the fallback is off, so turning it on later needs no
+    # second config change.
+    upstreams = str(tar1090_config.get('adsb_upstreams') or 'https://api.adsb.lol').strip()
+    lines.append(f"ADSB_UPSTREAMS={upstreams}\n\n")
 
     # External ADS-B feed for readsb
     adsb_source = tar1090_config.get('adsb_source', '')
diff --git a/config-merger/test/test_merge_config.py b/config-merger/test/test_merge_config.py
index 0138a79..d87d02c 100755
--- a/config-merger/test/test_merge_config.py
+++ b/config-merger/test/test_merge_config.py
@@ -1014,6 +1014,40 @@ def test_tracker_removal_does_not_rewrite_user_yml(self):
         self.assertEqual(user['network']['ports']['track'], 3003)
 
 
+    def test_upstream_chain_written_to_env(self):
+        """The chain reaches the proxy as ADSB_UPSTREAMS"""
+        self.write_yaml(os.path.join(self.defaults_dir, 'default.yml'), {
+            'tar1090': {
+                'adsblol_fallback': True,
+                'adsb_upstreams': 'https://adsb.retina.fm,https://api.adsb.lol',
+                'location': {'latitude': 42.2, 'longitude': -72.7, 'altitude': 80},
+            }
+        })
+        self.write_yaml(os.path.join(self.defaults_dir, 'forced.yml'), {})
+
+        self.run_merge()
+
+        with open(os.path.join(self.config_dir, 'tar1090.env')) as f:
+            env = f.read()
+        self.assertIn('ADSB_UPSTREAMS=https://adsb.retina.fm,https://api.adsb.lol\n', env)
+
+    def test_upstream_chain_falls_back_to_adsblol_when_unset(self):
+        """A config predating the key still produces a usable chain"""
+        self.write_yaml(os.path.join(self.defaults_dir, 'default.yml'), {
+            'tar1090': {
+                'adsblol_fallback': True,
+                'location': {'latitude': 42.2, 'longitude': -72.7, 'altitude': 80},
+            }
+        })
+        self.write_yaml(os.path.join(self.defaults_dir, 'forced.yml'), {})
+
+        self.run_merge()
+
+        with open(os.path.join(self.config_dir, 'tar1090.env')) as f:
+            env = f.read()
+        self.assertIn('ADSB_UPSTREAMS=https://api.adsb.lol\n', env)
+
+
 class TestAtomicWrites(unittest.TestCase):
     """The compose .env must be replaced whole, never rewritten in place.
 
diff --git a/config/default.yml b/config/default.yml
index 50cad7c..e31ec00 100644
--- a/config/default.yml
+++ b/config/default.yml
@@ -120,6 +120,11 @@ tar1090:
   adsb_source: ""  # Optional local ADS-B receiver (IP,PORT,PROTOCOL). Empty = rely on adsblol_fallback.
   adsblol_fallback: true
   adsblol_radius: 40
+  # Ordered, comma-separated list of adsb.lol-format sources the tar1090 proxy
+  # tries until one answers. A local receiver still wins over all of them.
+  # adsb.lol refuses ~88% of a node's requests with 429, so RETINA's own
+  # service goes first and adsb.lol sits behind it.
+  adsb_upstreams: "https://adsb.retina.fm,https://api.adsb.lol"
 
 # retina-tracker sidecar (github.com/offworldlabs/retina-tracker) config.
 # blah2 has no built-in tracker of its own; this sidecar does all tracking.
diff --git a/docker-compose.yml b/docker-compose.yml
index 32b3565..c264dd8 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -120,6 +120,7 @@ services:
       - TAR1090_DEFAULTCENTERLON=${RECEIVER_LON:-0}
       # adsb.lol proxy config
       - ADSBLOL_ENABLED=${ADSBLOL_ENABLED:-false}
+      - ADSB_UPSTREAMS=${ADSB_UPSTREAMS:-https://api.adsb.lol}
       - RECEIVER_LAT=${RECEIVER_LAT:-0}
       - RECEIVER_LON=${RECEIVER_LON:-0}
       - ADSBLOL_RADIUS=${ADSBLOL_RADIUS:-40}
diff --git a/staging/docker-compose.staging.yml b/staging/docker-compose.staging.yml
index d19f36b..f770e99 100644
--- a/staging/docker-compose.staging.yml
+++ b/staging/docker-compose.staging.yml
@@ -106,6 +106,7 @@ services:
       - TAR1090_DEFAULTCENTERLON=${RECEIVER_LON:--84.65191}
       # adsb.lol proxy config
       - ADSBLOL_ENABLED=${ADSBLOL_ENABLED:-true}
+      - ADSB_UPSTREAMS=${ADSB_UPSTREAMS:-https://api.adsb.lol}
       - RECEIVER_LAT=${RECEIVER_LAT:-33.939182}
       - RECEIVER_LON=${RECEIVER_LON:--84.65191}
       - ADSBLOL_RADIUS=${ADSBLOL_RADIUS:-40}