My Beloved watches a lot of shows about true airline tragedies and (listening in the background) I notice that a majority of the time when the tower is asking how many people are on the plane they ask “How many souls on board?”, with the response being something like “There are (fill in the blank) souls on board”. Why is “souls” the accepted terminology when it comes to asking about how many people there are on the plane?
Danny Glover ( not the actor ) suggests it’s official FAA terminology from 30~40 years ago but has since fallen out of favor.
Some people at the FAA Academy recall an FAA form titled “Inflight Emergency Checklist and Record” using the term “souls on board” until the early 1990s, but it now says “Number POB,” short for “persons on board.” It was revised both because of concerns about the shorthand “SOB” and about the word “souls” being interpreted as passengers who died.
Wayne Coley, who became a controller in 1984 and currently teaches at the FAA Academy, remembers being trained to say “souls on board” but added, “It’s no longer taught and hasn’t been taught for quite a while.”
As I understand it, it’s to 1: make i clear that they want just an absolute number of human beings so the pilot gives the correct number including staff and themself 2: Make it clear that this number is about living people and not dead bodies that may be onboard.
It might not be taught but I have a slight addiction to listening to Air Traffic chat of planes that are in trouble and they almost always ask for the number of souls on board.
My recollection is that it’s an old nautical usage, from a time where religiosity was endemic.
Interesting essay examining the history of the phrase “souls on board”:
A more purely philological perspective is from the Oxford English Dictionary. Scroll down to see citations at phrase definition 13a for “soul” as synonym or synecdoche for a person:
https://www.oed.com/oed2/00231475
Citations go back to ca. 11th Century in Old English, and recognizably modern English to the 17th Century.
It helps ARFF know how many they’re looking for if an emergency becomes a crash. People die, sometimes they die while flying on planes. Sometimes they die wherever they were & are being shipped back to their home/final destination in cargo. The guy who had a heart attack somewhere over the Atlantic or the body in the casket would be a body they are not souls as they are ‘soulless’ so they wouldn’t be counted.
Hmmm, using those criteria, they shouldn’t count my ex either. 
where? (or do I mean “how”?)
At one time, wasn’t the crew of a sailing ship separated into officers and people? If a ship went down with all aboard, stating how many “people” had died would be problematic. “Soul” could be used as a catchall.
Interesting side note: I just recently passed through a very small rural town and on the city limit sign they had the population listed in “souls”.
IME/IMO, it’s just the standard buzz-phrase. Like most idioms, it has some basis in long-lost logic, but now it’s just a collection of syllables with an agreed-upon meaning. I can’t add anything to the various speculations and citations others have already provided
Widening the scope just a bit … ATC generally wants to know four things about an emergency in progress which they use for their own planning and/or pass along to the ground emergency response folks for their planning:
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Headcount of live people. Mostly to stage an appropriately scaled ambulance response. If post-landing the pilots are disabled, that also helps them start an early accounting of the living and dead. If the pilots are undamaged, headcount aboard is one of the first things the fire responders will ask the pilots. For the same reason. To know when they’ve rounded up everybody and there’s nobody unaccounted for wandering the wilds of the airport or trapped under wreckage or …
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Fuel quantity on board measured in duration so they have some idea of how long this drama might last, or said another way, how urgent finding a runway is, and how urgently the ground forces need to prepare for the aircraft’s arrival.
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Fuel quantity on board measured in pounds (or kilos in MetricWorld) so the firefighters have some idea of how ginormous a conflagration they might be facing, and the enviro-cleanup folks know how big of an environmental mess they might be dealing with.
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Any functional impairments of the aircraft. Can’t navigate, must land fast, can’t climb well, can’t stop well, on fire, etc.
Just go to YouTube and search for “atc emergency.”
it’s amazing anybody gets anything done, you know what I mean?
My first career was as an airport firefighter. Left as a deputy chief. The fascination and intensity with which ATC and many firefighters want fuel on board numbers used to drive me nuts. If there’s a fire, put it out. The end. You’re bringjng enough foam to the party to put out all of the fire within 75 feet of the fuselage (or what’s left of it). It isn’t like we’re changing the response based on fuel quantities, its the same equipment whether its 5 gallons or 50,000 gallons. And if it goes down a storm drain or into the dirt, its all going to get picked up anyways.
And the guys who can’t think in pounds and want the pilot to convert to gallons - um, they’re busy doing real stuff right now. Just divide the pounds by 7 and you’ll be close enough.
The only time it matters if if the problem is low fuel, then we know they might not land on the airport (then it’s someone else’s problem!).
Once I was in charge, I did make some headway in decreasing the emphasis on fuel remaining, but those habits are tough to wring out of people.
Excellent to hear straight from the other end of the response team. Thank you.
Way back when I was learning all this stuff I wondered why fuel quantity was so important. Heck, given an airplane type or even just general size classification you can just assume worst case based on published fuel capacity from a quick reference sheet in your response handbook. It’s not like an extra couple hundred or even thousand gallons is going to greatly alter the situation. The vagaries of how much damage and how much spillage has a lot larger impact on the actual problem you need to solve than does how much we’re carrying.
I wonder if fuel quantity was a bigger deal in the 1950s when fire apparatus and airport fire companies were not nearly as capable as they are today and when large airplanes were carrying the rather more dangerous avgas, not jet fuel. And perhaps now the tradition is pointlessly carried on, like cutting the end off the roast because Grandma said her Mom used to do it.
TIL pretzels are soul food.
Broadcastify has a few airport feeds but I imagine one could listen for quite a while before anything interesting happens. 
Example:
Anchorage International
Is the “Souls on board and fuel?” question and response formalized/standardized in training?
In those ATC videos it seems pretty much standard that ATC asks for “souls and fuel on board when you get a chance”, then at some point the pilot reports their fuel in minutes followed by ATC asking for it in pounds.
It could be that ATC wants it in both, but it always sounds like two different points of view (pilots really only care how long/far they can fly with it, while firefighters couldn’t care less about the efficiency of the engines and only want to know how much there is).
About a decade ago, an Asiana Airlines flight crashed while landing at San Francisco. I heard that one passenger, a teenage girl, was killed because she was sitting or lying on the ground next to the plane, obscured by the firefighting foam, and was run over by one of the fire trucks. However, the Wikipedia summary of the story says that she was already dead. Still pretty gruesome.
I suspect the pilots are interested in how much weight the fuel adds to the aircraft.
VASAviation is a channel devoted to ATC communications. Usually emergencies, but the also have collections of funny chatter, as well - there was a now-retired controller at JFK International named “Kennedy Steve” Abraham who was famous for his quips.
VASAvation videos are, I would think, a good cure for fear of flying; listening to them, you realize just how calm, unflappable, and competent professional pilots and ATC controllers are.