A short list of internationally recognized distress signals worth memorizing cold, since you may not have time to improvise one under stress:
- SOS — in any medium (light, sound, radio): three short, three long, three short. It's recognized worldwide regardless of language.
- Rule of threes — three of any signal (shots, whistle blasts, fire flashes) means distress; responding with one signal means "message received."
- Ground-to-air body signals — arms raised in a "Y" shape means "need assistance"; arms held straight out means "unable to proceed," useful if you can't build ground symbols but a search aircraft can see you directly.
- Ground-to-air symbols (V, X, arrow): V = need assistance, X = need medical assistance, arrow = direction you're proceeding.
- Orange or brightly colored panels/clothing laid flat and large — color contrast against terrain matters more than the specific shape if you don't know the formal symbol set.
The signal only works if it's sustained and visible — a single wave or a symbol that blends into the ground at altitude won't register. Build big, keep contrast high, and repeat.