1.   At the time, a Korean Air Lines freighter in the area had signaled an emergency, which later turned out to be the result of low fuel.

2.   She will have locks on her doors and a horn to signal emergencies.

3.   The International Space Station will be so noisy that astronauts may struggle to communicate, suffer poor health and even miss crucial warning tones that signal an emergency.

4.   Then a siren blared, signaling an emergency on the track.