What should be your first reaction upon seeing a flashing red light while on the runway?

When encountering a flashing red light while on the runway, the appropriate response is to clear the taxiway or runway. This signal typically indicates that there is a serious hazard or an imminent danger in the area, prompting immediate action to ensure safety. Clearing the runway helps prevent potential collisions with aircraft or other vehicles and allows for a safe environment for any emergency or ongoing operations.

Other options, such as starting engine checks or beginning to taxi, could exacerbate the situation by increasing risks associated with being in a dangerous area. Contacting the tower, while an important communication step, should come after ensuring that you have cleared any hazardous area. Therefore, prioritizing safety by immediately moving away from the runway in response to a flashing red light is crucial.