Signals work by breaking the pattern of the natural environment — straight lines, bright colors, and repeated rhythms all read as "not natural" from a distance, which is exactly what you want a rescuer to notice.
Visual, daytime:
- Signal mirrors can be seen for miles in good sun — aim by holding a hand out, sighting the target through the mirror's aim hole, and adjusting until the light spot lands on your hand.
- Ground-to-air symbols: large, high-contrast shapes (branches, rocks, trampled snow) at least 10 ft across, built in an open area visible from above.
- Smoke by day (add green material to a fire for thick white smoke), flame by night.
Visual, nighttime: A steady light source is harder to place than a blinking one — flashing (even just waving a flashlight) reads as deliberate and human far more reliably than a static glow.
Audio: Three of anything — three whistle blasts, three shots, three shouts — is the internationally recognized distress pattern. One blast means "I hear you, where are you"; keep the distress pattern of three as the ask for help.
Stay in one place once you've started signaling, if possible — a moving target is far harder for search teams to relocate.