diff --git a/protobufs/atc/v1/event.proto b/protobufs/atc/v1/event.proto
index 3940a5a..48aea9f 100644
--- a/protobufs/atc/v1/event.proto
+++ b/protobufs/atc/v1/event.proto
@@ -6,6 +6,11 @@ import "atc/v1/airplane.proto";
 import "atc/v1/location.proto";
 import "atc/v1/node.proto";
 
+message AirplaneCollided {
+  string id1 = 1;
+  string id2 = 2;
+}
+
 message AirplaneDetected {
   Airplane airplane = 1;
 }
@@ -32,12 +37,13 @@ message StreamRequest {}
 
 message StreamResponse {
   oneof event {
-    AirplaneDetected airplane_detected = 1;
-    AirplaneLanded airplane_landed = 2;
-    AirplaneMoved airplane_moved = 3;
-    FlightPlanUpdated flight_plan_updated = 4;
-    GameStarted game_started = 5;
-    GameStopped game_stopped = 6;
+    AirplaneCollided airplane_collided = 1;
+    AirplaneDetected airplane_detected = 2;
+    AirplaneLanded airplane_landed = 3;
+    AirplaneMoved airplane_moved = 4;
+    FlightPlanUpdated flight_plan_updated = 5;
+    GameStarted game_started = 6;
+    GameStopped game_stopped = 7;
   }
 }
 
diff --git a/src/atc-game/src/components/airplane.rs b/src/atc-game/src/components/airplane.rs
index 8154429..5f03650 100644
--- a/src/atc-game/src/components/airplane.rs
+++ b/src/atc-game/src/components/airplane.rs
@@ -1,5 +1,7 @@
 use bevy::prelude::*;
 
+pub const AIRPLANE_SIZE: f32 = 24.0;
+
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Default, Component)]
 pub struct Airplane;
 
diff --git a/src/atc-game/src/components/collider.rs b/src/atc-game/src/components/collider.rs
new file mode 100644
index 0000000..8d8f576
--- /dev/null
+++ b/src/atc-game/src/components/collider.rs
@@ -0,0 +1,21 @@
+use bevy::prelude::*;
+
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Default, Component)]
+pub struct Collider;
+
+#[cfg(test)]
+mod tests {
+    use super::Collider;
+
+    #[test]
+    fn trait_send() {
+        fn assert_send<T: Send>() {}
+        assert_send::<Collider>();
+    }
+
+    #[test]
+    fn trait_sync() {
+        fn assert_sync<T: Sync>() {}
+        assert_sync::<Collider>();
+    }
+}
diff --git a/src/atc-game/src/components/mod.rs b/src/atc-game/src/components/mod.rs
index 2370f08..24bdfa3 100644
--- a/src/atc-game/src/components/mod.rs
+++ b/src/atc-game/src/components/mod.rs
@@ -1,11 +1,13 @@
 pub use self::airplane::*;
 pub use self::airplane_id::*;
+pub use self::collider::*;
 pub use self::flight_plan::*;
 pub use self::location::*;
 pub use self::speed::*;
 
 mod airplane;
 mod airplane_id;
+mod collider;
 mod flight_plan;
 mod location;
 mod speed;
diff --git a/src/atc-game/src/event/mod.rs b/src/atc-game/src/event/mod.rs
index ecd24f4..e302424 100644
--- a/src/atc-game/src/event/mod.rs
+++ b/src/atc-game/src/event/mod.rs
@@ -1,7 +1,7 @@
 use atc::v1::stream_response::Event as ApiEvent;
 use atc::v1::{
-    Airplane, AirplaneDetected, AirplaneLanded, AirplaneMoved, FlightPlanUpdated, GameStarted,
-    GameStopped,
+    Airplane, AirplaneCollided, AirplaneDetected, AirplaneLanded, AirplaneMoved, FlightPlanUpdated,
+    GameStarted, GameStopped,
 };
 
 use crate::api::IntoApi;
@@ -13,6 +13,7 @@ mod bus;
 
 #[derive(Clone, Eq, PartialEq, Hash, Debug)]
 pub enum Event {
+    AirplaneCollided(AirplaneId, AirplaneId),
     AirplaneDetected(AirplaneId, Location, FlightPlan),
     AirplaneLanded(AirplaneId),
     AirplaneMoved(AirplaneId, Location),
@@ -26,6 +27,12 @@ impl IntoApi for Event {
 
     fn into_api(self) -> Self::ApiType {
         match self {
+            Event::AirplaneCollided(airplane_id1, airplane_id2) => {
+                ApiEvent::AirplaneCollided(AirplaneCollided {
+                    id1: airplane_id1.into_api(),
+                    id2: airplane_id2.into_api(),
+                })
+            }
             Event::AirplaneDetected(id, location, flight_plan) => {
                 ApiEvent::AirplaneDetected(AirplaneDetected {
                     airplane: Some(Airplane {
diff --git a/src/atc-game/src/state/running.rs b/src/atc-game/src/state/running.rs
index d40436f..788f65d 100644
--- a/src/atc-game/src/state/running.rs
+++ b/src/atc-game/src/state/running.rs
@@ -4,8 +4,8 @@ use atc::v1::get_game_state_response::GameState;
 
 use crate::event::{Event, EventBus};
 use crate::systems::{
-    despawn_airplane, follow_flight_plan, setup_airport, setup_grid, spawn_airplane,
-    update_flight_plan, SpawnTimer,
+    despawn_airplane, detect_collision, follow_flight_plan, setup_airport, setup_grid,
+    spawn_airplane, update_flight_plan, SpawnTimer,
 };
 
 pub struct GameStateRunningPlugin;
@@ -22,11 +22,12 @@ impl Plugin for GameStateRunningPlugin {
             .add_system_set(
                 SystemSet::on_update(GameState::Running)
                     .with_system(despawn_airplane)
-                    .with_system(follow_flight_plan)
+                    .with_system(follow_flight_plan.label("movement"))
                     .with_system(spawn_airplane)
-                    .with_system(update_flight_plan),
+                    .with_system(update_flight_plan)
+                    .with_system(detect_collision.after("movement")),
             )
-            .add_system_set(SystemSet::on_exit(GameState::Running));
+            .add_system_set(SystemSet::on_exit(GameState::Running).with_system(despawn_entities));
     }
 }
 
@@ -36,3 +37,9 @@ fn send_event(event_bus: Local<EventBus>) {
         .send(Event::GameStarted)
         .expect("failed to send event"); // TODO: Handle error
 }
+
+fn despawn_entities(mut commands: Commands, query: Query<Entity, Without<Camera>>) {
+    for entity in query.iter() {
+        commands.entity(entity).despawn_recursive();
+    }
+}
diff --git a/src/atc-game/src/store/watcher.rs b/src/atc-game/src/store/watcher.rs
index 3d21a2f..c5223bc 100644
--- a/src/atc-game/src/store/watcher.rs
+++ b/src/atc-game/src/store/watcher.rs
@@ -29,6 +29,7 @@ impl StoreWatcher {
                 Event::FlightPlanUpdated(id, flight_plan) => {
                     self.update_flight_plan(id, flight_plan);
                 }
+                Event::GameStopped => self.reset(),
                 _ => {}
             }
         }
@@ -60,4 +61,8 @@ impl StoreWatcher {
             airplane.flight_plan = flight_plan.into_api();
         }
     }
+
+    fn reset(&self) {
+        self.store.clear();
+    }
 }
diff --git a/src/atc-game/src/systems/detect_collisions.rs b/src/atc-game/src/systems/detect_collisions.rs
new file mode 100644
index 0000000..72c71ed
--- /dev/null
+++ b/src/atc-game/src/systems/detect_collisions.rs
@@ -0,0 +1,55 @@
+use bevy::prelude::*;
+use bevy::sprite::collide_aabb::collide;
+
+use atc::v1::get_game_state_response::GameState;
+
+use crate::components::{AirplaneId, Collider, AIRPLANE_SIZE};
+use crate::event::{Event, EventBus};
+
+pub struct Size {
+    airplane: Vec2,
+}
+
+impl Default for Size {
+    fn default() -> Self {
+        Self {
+            airplane: Vec2::new(AIRPLANE_SIZE, AIRPLANE_SIZE),
+        }
+    }
+}
+
+pub fn detect_collision(
+    mut app_state: ResMut<State<GameState>>,
+    query: Query<(Entity, &AirplaneId, &Collider, &Transform)>,
+    event_bus: Local<EventBus>,
+    size: Local<Size>,
+) {
+    'outer: for (entity1, airplane_id1, _, transform1) in query.iter() {
+        for (entity2, airplane_id2, _, transform2) in query.iter() {
+            if entity1 == entity2 {
+                continue;
+            }
+
+            if collide(
+                transform1.translation,
+                size.airplane,
+                transform2.translation,
+                size.airplane,
+            )
+            .is_some()
+            {
+                event_bus
+                    .sender()
+                    .send(Event::AirplaneCollided(
+                        airplane_id1.clone(),
+                        airplane_id2.clone(),
+                    ))
+                    .expect("failed to send event"); // TODO: Handle error
+
+                app_state.set(GameState::Ready).unwrap();
+
+                break 'outer;
+            }
+        }
+    }
+}
diff --git a/src/atc-game/src/systems/mod.rs b/src/atc-game/src/systems/mod.rs
index 41e82e5..197501a 100644
--- a/src/atc-game/src/systems/mod.rs
+++ b/src/atc-game/src/systems/mod.rs
@@ -1,5 +1,6 @@
 pub use self::change_app_state::*;
 pub use self::despawn_airplane::*;
+pub use self::detect_collisions::*;
 pub use self::follow_flight_plan::*;
 pub use self::setup_airport::*;
 pub use self::setup_cameras::*;
@@ -9,6 +10,7 @@ pub use self::update_flight_plan::*;
 
 mod change_app_state;
 mod despawn_airplane;
+mod detect_collisions;
 mod follow_flight_plan;
 mod setup_airport;
 mod setup_cameras;
diff --git a/src/atc-game/src/systems/spawn_airplane.rs b/src/atc-game/src/systems/spawn_airplane.rs
index 1ed8bf3..4d965a7 100644
--- a/src/atc-game/src/systems/spawn_airplane.rs
+++ b/src/atc-game/src/systems/spawn_airplane.rs
@@ -1,7 +1,9 @@
 use bevy::prelude::*;
 use rand::Rng;
 
-use crate::components::{Airplane, AirplaneIdGenerator, FlightPlan, Location, Speed};
+use crate::components::{
+    Airplane, AirplaneIdGenerator, Collider, FlightPlan, Location, Speed, AIRPLANE_SIZE,
+};
 use crate::map::{route_between, Tile, MAP_HEIGHT_RANGE, MAP_WIDTH_RANGE};
 use crate::{Event, EventBus};
 
@@ -32,7 +34,7 @@ pub fn spawn_airplane(
             .spawn_bundle(SpriteBundle {
                 transform: Transform {
                     translation: Vec3::new(spawn_point.x(), spawn_point.y(), 2.0),
-                    scale: Vec3::new(8.0, 8.0, 0.0),
+                    scale: Vec3::new(AIRPLANE_SIZE, AIRPLANE_SIZE, 0.0),
                     ..Default::default()
                 },
                 sprite: Sprite {
@@ -43,6 +45,7 @@ pub fn spawn_airplane(
             })
             .insert(Airplane)
             .insert(airplane_id.clone())
+            .insert(Collider)
             .insert(flight_plan.clone())
             .insert(Speed::new(32.0));
 
diff --git a/src/print-client/src/main.rs b/src/print-client/src/main.rs
index 6f0ee1e..9fcd9d2 100644
--- a/src/print-client/src/main.rs
+++ b/src/print-client/src/main.rs
@@ -6,6 +6,7 @@ use atc::v1::StreamRequest;
 
 fn should_print(event: &Event) -> bool {
     match event {
+        Event::AirplaneCollided(_) => true,
         Event::AirplaneDetected(_) => true,
         Event::AirplaneLanded(_) => true,
         Event::AirplaneMoved(_) => false,
@@ -29,6 +30,12 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         }
 
         match event {
+            Event::AirplaneCollided(collision) => {
+                println!(
+                    "Airplane {} collided with airplane {}",
+                    collision.id1, collision.id2
+                );
+            }
             Event::AirplaneDetected(airplane_detected) => {
                 let airplane = airplane_detected.airplane.unwrap();
                 let location = airplane.location.unwrap();