- Hearing a continuous or unfamiliar engine-like sound in the sky.
- Noticing a flying object at a low altitude.
- Seeing a flying object moving at a constant speed or along an unusual path.
- The sound continued briefly before disappearing.
- Noticing moving lights in the sky.
The presence of such signs does not necessarily mean there is danger; however, it is always advisable to follow precautionary guidance or any official instructions as a preventive measure.
