I am researching for a book and would like to know how a commercial aircraft would signal that his aircraft has an emergency. Not mechanical or violence, but possible biological contamination.

What is the protocol for such an event and what such dialog might exchange between the pilots and ATC?

Any advise would help.


  • $\begingroup$ In addition to speaking to ATC, the crew in such a situation may consult a medical advisory service, such as MedLink, which would allow them to talk to emergency physicians by satellite phone. $\endgroup$ Sep 21, 2018 at 6:50
  • $\begingroup$ Okay, thanks, Zach. I appreciate your comments. $\endgroup$ Sep 21, 2018 at 6:53
  • $\begingroup$ @Harper the OP never said the pilots would know its biological and understand everything about it. It doesn’t take a Doctor to notice that several people have become very ill very quickly and that they need urgent medical attention. $\endgroup$
    – Notts90
    Sep 21, 2018 at 7:14

1 Answer 1


The procedure would likely be the same as any other medical emergency: get the plane on the ground (which is a thing that pilots are good at doing, and have the training and skills to do) so that the medical crews can handle the medical emergency (which is a thing that pilots are not good at doing, and have neither training nor skills to do)

The initial radio call might be something along the lines of "Mayday mayday mayday, Oceanic 201 requesting immediate vector to LAX for a medical emergency, multiple passengers"

  • "Mayday" indicates several things all at once.
    1. "Everyone else currently on this radio frequency, shut up."
    2. "I am in the middle of an emergency, therefore I am now the most important person in the sky."
    3. "I will do whatever I need to in order to keep this plane safe. Air traffic controllers, you will get everyone else out of my way."
    4. Saying it three times has no relevance other than to make sure that it's heard and the number three indicates distress in general.
  • "Oceanic 201" is the callsign of the aircraft.
  • "Requesting" is used to tell ATC that the crew requires action from them, in this case a vector to a suitable airport.
  • "for a medical emergency, multiple passengers" prepares the emergency crews for whatever situation they're about to have dropped in their laps.

For further examples of cockpit-to-ATC communication under critical circumstances, you might find it helpful to read the cockpit voice recorder transcript of United flight 232, or other in-flight emergency transcripts.

  • $\begingroup$ Thank you, Steve V. for your very helpful response! I will research your link as well. Much appreciated! :D $\endgroup$ Sep 21, 2018 at 6:41
  • $\begingroup$ This is correct. Also, although the pilot will request vectors if there is time for a request and approval, if the emergency demanded an immediate turn, the pilot will start the turn and tell ATC what they are doing (rather than asking permission). As noted in this answer, the regulations permit the pilot do whatever they need to save lives, with or without prior ATC approval. But if time permits, letting ATC give you the vectors is safer, because it gives them time to get other traffic out of your way. $\endgroup$ Sep 21, 2018 at 9:47
  • $\begingroup$ Isn't there a camera outside the cockpit door for them to see who is behind it? $\endgroup$ Sep 21, 2018 at 11:41
  • $\begingroup$ "Saying it three times has no relevance other than to make sure that it's heard and the number three indicates distress in general." - Saying it three times also indicates that you're actually declaring an emergency, rather than simply mentioning the word in some other context. You might say something like "we heard a mayday call" or "request taxi instructions to Mayday Avionics" over the radio, but you'd probably never say "mayday, mayday, mayday" except when declaring an emergency. $\endgroup$ Sep 21, 2018 at 22:02
  • 3
    $\begingroup$ @TannerSwett - The day they elect me king of Earth, i'm telling Mayday avionics that they need to change their name. $\endgroup$
    – Steve V.
    Sep 22, 2018 at 3:16

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