We often debate the viability, practically, and benefit of social distancing on airplanes. But what does the science say blocking middle seats?
The Science Behind Social Distancing + Middle Seat Blocking Onboard Airplanes
Live and Let’s Fly has a wide readership, including in the scientific community. One reader took the time to write a very thoughtful note and detailed argument for why social distancing, even if it is only an open middle seats, does play an important role in slowing the spread of virus.
I’m not a scientist and I have no way, beyond applying my layman knowledge of the subject, to critically review the argument below. But I present you excerpts from the letter, which is certainly worthy of our consideration.
First, the scientist established their credentials, also expressing “concern that you are inadvertently misleading your readers about the risk factors associated with the lack of in-flight social distancing.”
The issue is not whether six feet of social distancing is possible, but whether blocked middle seats provide enough additional protection to justify keeping them open.
I agree with you that it is impossible to maintain six feet social distancing on planes. I also agree with you that airlines will lose money on every flight if they block middle seats and maintain the current fares, and it is unreasonable to shame airlines for selling their flights full in a competitive marketplace where customers will just book with your competitors if you charge a 50% premium for social distancing.
I strongly disagree that there is no value in blocking middle seats; in fact I would strongly advocate that all airlines be forced to block middle seats, either through public pressure or a federal mandate. I would hope that this would create upward pressure on prices, especially since the reduced demand currently present is comprised of travelers who really need to travel and thus likely less sensitive to prices. I would be open to increased government aid as well. But since you have a large readership, hopefully people like you can do your part in better informing customers so that they can vote with their wallet and pressure United and American to match Delta in blocking middle seats.
I am not trying to raise any hysteria. I myself flew multiple times during the pandemic to see loved ones. I understand that airplanes are actually one of the safest environments among various modes of mass transportation. They have clean filtered air that flows from top to bottom, and the rate of circulation is high enough that the viral load is significantly reduced even in the presence of an infected patient. But right now, all mass transportation poses a significant risk, airplanes included.
Here’s the key part that I think you are missing: social distancing is not a binary between six feet or nothing. We have some decent data on the efficacy of various levels of social distancing, and we also have research on how viruses spread within airplanes. Because of the air flow pattern in an airplane, only passengers in close proximity to an infected passenger are significantly at risk (unless he or she has some other close interaction during in-flight service or boarding).
A good rule of thumb is that infection risk seems to approximately fall by half with every 0.5 meters of distance. So the seat next to you at 0.5 meters is twice the risk of the one at 1.0 meters, and generally speaking, about 1.5 meters of social distancing seems barely enough to mitigate the spread of the virus enough so that it does not spread exponentially.
So let’s pick an example: a 737 jet with 32-inch seat pitch and 17.5-inch wide seats and a 20-inch aisle.
1. Delta, 60% capacity, window seats:
0 person at 0.0~0.5m (x4), 2.7 persons at 0.5~1.0m (x2), 1.8 persons at 1.0~1.5m
= equivalent of 7.2 persons at 1.0~1.5m distance
2. Delta, 60% capacity, aisle seats:
0 person at 0.0~0.5m (x4), 3.6 persons at 0.5~1.0m (x2), 3.6 persons at 1.0~1.5m
= equivalent of 10.8 persons at 1.0~1.5m distance
3. United, 100% capacity, window seats:
1 person at 0.0~0.5m (x4), 5 persons at 0.5~1.0m (x2), 2 persons at 1.0~1.5m
= equivalent of 16 persons at 1.0~1.5m distance
4. United, 100% capacity, aisle seats:
1 person at 0.0~0.5m (x4), 6 persons at 0.5~1.0m (x2), 5 persons at 1.0~1.5m
= equivalent of 21 persons at 1.0~1.5m distance
5. United, 100% capacity, middle seats:
2 persons at 0.0~0.5m (x4), 6 persons at 0.5~1.0m (x2), 1 persons at 1.0~1.5m
= equivalent of 21 persons at 1.0~1.5m distance
Thus, an average Delta customer faces the risk equivalent of 9 persons at 1.0~1.5m distance, and an average United customer faces the risk equivalent of 19.3 persons at 1.0~1.5m distance. An average United customer faces more than twice as much risk on board as an average Delta customer. You might think a factor of two is not significant, but because an epidemic grows exponentially, a factor of two can make the difference between an exploding epidemic and a decaying one. If the R0 value [basic reproduction number] of COVID-19 is around 2.5, and universal mask wearing cuts the risk factor a bit (even if planes are slightly higher risk than the average environment), further reduction by another factor of two can bring the R value below 1.0, and we know that exponents below 1.0 eventually decay to zero.
This is obviously a very rough back-of-the-envelope calculation intended to be an illustrative example, but proper researchers in the field have run much more sophisticated epidemics models with real-world statistics and computer simulations.
More Resources On The Science Behind Middle Seat Blocking
The scientist recommended two further sources to explore this issue:
- Scientists know ways to help stop viruses from spreading on airplanes. They’re too late for this pandemic.
- At least 3 feet of social distancing likely reduces COVID-19 spread, study confirms
This morning, I also happened to read another story on this topic in ZDnet which chronicles the research of MIT scholar Arnold Barnett and makes many of the arguments made above. It also helps to explain risk:
The average risk of catching COVID-19 from flying on a plane is 1 in 4,300, according to Barnett’s model. That rate is roughly double the risk if airlines were to leave the middle seat open, 1 in 7,700, Barnett estimates. Using a relatively low fatality rate of 1% of all people who contract COVID-19, he estimates, means that the 1 in 4,300 risk of catching COVID-19 turns into a risk of dying from the disease of 1 in 430,000. That is much more likely than the standard measure of risk of dying by airplane crash, which is 1 in 34 million.
Does a risk level of this nature even matter?
With 200,000 passengers per day being carried by the major U.S. airlines over the next three months, a total of perhaps 18 million passengers will be carried in the U.S. at the current rate of bookings, he explained. Going from the 1 in 7,700 Covid-19 risk per passenger with the middle seat filled to just 1 in 4,300 with it empty would avert 1,800 Covid-19 infections, he argues, and 18 potential deaths at a fatality rate of 1%.
Using a value of $9 million for a human life, which is a figure described by Boston University researcher Austin Frakt as roughly the value U.S. government agencies use, the dollar equivalent of the 18 lost lives would be about $173 million.
“It is hard to imagine that the cost to American Airlines and United of averting those deaths would be anywhere near $173 million in the coming months,” Barnett said.
The entire article is quite interesting:
- Filling middle seats nearly doubles airline passenger risk of catching COVID-19, says MIT researcher
It is my goal to always use my platform of Live and Let’s Fly in a responsible manner. I’ve long discounted the benefit of leaving middle seats opens, but we clearly see that our calculus should not be six feet or nothing. Instead, we must continue to weigh risks and note the likely incremental benefits of even a few inches. I’m still not ready to advocate for mandatory middle seat blocking. But my continuing research on the matter is helping me–and will hopefully help you–more smartly think about this topic.