| Clue | Source | Date |
|---|---|---|
| Warning during the Blitz | Thomas Joseph | 09 Jul 2025 |
| Sortie signal | Premier Sunday | 16 Jun 2024 |
| Noise heard during the London Blitz | New York Times | 07 Feb 2021 |
| Warning during the Battle of Britain | New York Times | 05 Jun 2020 |
| Signal to pilots | Premier Sunday | 22 May 2016 |
| Wartime signal | ||
| Signal that starts a scramble | ||
| Pre-sortie signal | ||
| Fighter squadron's signal | ||
| Wartime warning | ||
| Pre-sortie signal | ||
| Sortie signal | ||
| Signal to combat pilots | ||
| Environmental warning | ||
| Warning during wartime |