diff --git a/changelog.d/1115-aircraft-altitude-band-unknown.md b/changelog.d/1115-aircraft-altitude-band-unknown.md
new file mode 100644
index 000000000..a6b69472d
--- /dev/null
+++ b/changelog.d/1115-aircraft-altitude-band-unknown.md
@@ -0,0 +1,2 @@
+- Exclude aircraft without a reported altitude from requested altitude bands;
+  unfiltered aircraft queries still retain them (rudycelekli, #1115).
diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index df92c0d50..1bdca7670 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -100,6 +100,9 @@ shared `area` argument (place name, bounding box, or point and radius) and cap
 lists at 25 rows by default. Voice offers the same queries next to its app
 actions: the session lists them, and the browser runs them through the same
 catalog, loaded on first use. See [tools and the MCP server](TOOLS.md).
+Aircraft altitude-band queries require a reported barometric or geometric altitude
+for each match, so a grounded contact that reports none is left out of a band too.
+Queries without an altitude band retain unknown-altitude contacts.
 
 Catalog calls check their cancellation signal immediately before executing a
 tool. Already-cancelled queries do not start; cancellation after execution starts
diff --git a/src/tools/queries/aviation.js b/src/tools/queries/aviation.js
index 0b8b54b79..235f542e1 100644
--- a/src/tools/queries/aviation.js
+++ b/src/tools/queries/aviation.js
@@ -111,6 +111,8 @@ export const aircraftInArea = defineTool({
         (record) =>
           areaContains(area, { lat: record.latitude, lon: record.longitude }) &&
           !(args.airborne_only && record.onGround) &&
+          ((args.min_altitude_m == null && args.max_altitude_m == null) ||
+            Number.isFinite(altitude(record))) &&
           (args.min_altitude_m == null ||
             altitude(record) >= args.min_altitude_m) &&
           (args.max_altitude_m == null ||
diff --git a/src/tools/queries/aviation.test.mjs b/src/tools/queries/aviation.test.mjs
index 20ec833aa..d0e979ed6 100644
--- a/src/tools/queries/aviation.test.mjs
+++ b/src/tools/queries/aviation.test.mjs
@@ -388,3 +388,62 @@ test('the real OpenSky source marks an hour-old snapshot stale for searches', as
   assert.deepEqual(result.data.stale_feeds, ['civil']);
   assert.match(result.summary, /may be stale\.$/);
 });
+
+test('altitude bands require a reported altitude from normalized OpenSky records', async () => {
+  const { normalizeOpenSkyAircraft } =
+    await import('../../sources/live/aircraft.js');
+  const state = (id, baro, geometric) =>
+    normalizeOpenSkyAircraft([
+      id,
+      'TEST',
+      'Test',
+      1767225600,
+      1767225600,
+      0,
+      0,
+      baro,
+      false,
+      10,
+      90,
+      0,
+      [],
+      geometric,
+    ]);
+  const records = [
+    state('abc001', null, null),
+    state('abc002', 0, null),
+    state('abc003', null, 50),
+    state('abc004', 500, null),
+  ];
+  const catalog = composeCatalog({
+    tools: coreTools,
+    services: {
+      aircraft: { getSnapshot: async () => ({ records }) },
+    },
+  });
+  const area = { bbox: [-1, -1, 1, 1] };
+  assert.equal(
+    (await catalog.call('aircraft_in_area', { area })).data.total,
+    4,
+    'unfiltered answers retain unknown altitude',
+  );
+  for (const band of [
+    { max_altitude_m: 100 },
+    { min_altitude_m: -500, max_altitude_m: 100 },
+  ]) {
+    const result = await catalog.call('aircraft_in_area', { area, ...band });
+    assert.deepEqual(
+      result.data.rows.map((row) => row.id),
+      ['abc002', 'abc003'],
+    );
+    assert.deepEqual(
+      result.data.rows.map((row) => row.altitude_m),
+      [0, 50],
+    );
+  }
+  const minimum = await catalog.call('aircraft_in_area', {
+    area,
+    min_altitude_m: -500,
+  });
+  assert.equal(minimum.data.total, 3);
+});