What air travelers need to know about middle seat blocking

With United and American Airlines now filling planes to capacity instead of continuing middle seat blocking, will that make their planes appreciably less safe?

Middle seat blockingIn the U.S., COVID-19 cases are nearing three million and deaths from the virus already exceed 132,000. Delta Air Lines, Southwest Airlines, and JetBlue Airways will continue to block middle seat reservations, United and American Airlines will start to book flights to aircraft capacity.

The Federation of American Scientists, in an open letter, urges United and American to reverse their decision. Of the decision, Dr. Anthony S. Fauci, Director of the National Institute of Allergy and Infectious Diseases, said he was concerned. The decision is problematic. Dr. Robert Redfield, Director of the CDC (Centers for Disease Control), said the change is a disappointment, but not a priority concern. Neither called for the CDC or FAA (Federal Aviation Administration) to mandate blocking passengers from booking middle seats to maximize the distance between passengers on planes.

Blocking the middle seat only separates airline passengers by about 18 inches.

Blocking the middle seat gives airline passengers about 18 inches, on average, between each other while in flight. That can help prevent virus transmission to a small degree. However, it isn’t what people understand is adequate “socially distancing,” something that’s not actually possible on planes.

Let’s look at the top issues of COVID-19 transmission and air travel.

The air in airplane cabins is highly filtered with HEPA filters.

Air circulation:

According to the CDC, “Most viruses and other germs do not spread easily on flights because of how air circulates and is filtered on airplanes.” Commercial aircraft today use HEPA filters, which capture 99.9 percent of particles including bacteria, fungi, and viruses in the 0.1 to 0.3-micron range. The COVID-19 particle size averages about 0.125 microns, but it’s typically bonded to something larger like respiratory droplets. So, COVID-19 can be filtered out by aircraft filters. Aircraft cabin air generally passes through the filters 20-30 times per hour.

Flight time:

The likelihood of becoming infected with COVID-19 depends on being close to a person infected with the virus and how long you’re near that person. The longer the flight, the more likely the virus can be transmitted to you from an infected person near you.

Social distancing:

The CDC recommends social distancing at six feet or more. On a plane, the typical distance between seats in a row is just 17–22 inches. Passengers sitting across the aisle from each other are normally 15–20 inches apart. Of course, every inch might help you avoid infection, but blocking off middle seats only results in a social distancing of about 31 percent of the CDC recommendation. Other prevention methods are therefore essential.

A passenger not wearing a face mask will expel their hard cough 6 feet in only 5 seconds.


The primary method of COVID-19 transmission is from person to person through respiratory droplets produced when an infected person coughs, sneezes, or talks. A lab at Florida Atlantic University did a simulation study to determine the effectiveness of face masks. The study focused on preventing the spread of respiratory droplets that could transmit COVID-19.

In the simulation, without a face mask, a heavy cough traveled 3 feet in about a second. The droplets associated with the cough traveled a further 6 feet within 5 seconds. Then they shot out another 9 feet within 10 seconds. The effects of the cough traveled about 12 feet overall before mostly dissipating. The droplets appeared significantly dense through 9 feet. Even a gentle cough traveled 3 feet quickly, without a mask. With a mask, the hard cough traveled less than 6 inches, even with a homemade type mask.

All the major airlines in the U.S. now require passengers to wear masks on board their planes, except when they are eating or drinking. Masks appear to be the most important preventive measure for the transmission of COVID-19 on airplanes.

Passengers must remove their face mask when eating or drinking in flight. This can be seriously problematic

Beverages and snacks:

Airlines, including those still blocking middle seats, are again serving beverages and snacks. That means that face masks will be removed when passengers drink and eat. During that time, noses and mouths will be free to expel respiratory droplets directly into aircraft cabin air when passengers cough, sneeze, talk or even chew. That is very troubling, even when middle seats aren’t occupied.


Airlines have substantially improved cleaning and disinfecting their aircraft. They are wiping down high touch areas of their planes with high-grade EPA-registered disinfectants and beginning to use highly effective disinfectant fogging processes.

Health questionnaires:

Airlines have begun to require passengers to answer health questionnaires at check-in. What percentage of passengers may lie on the form is unknown, but it requires travelers to at least consider potential problems about their health, that if they take seriously, will weed out some potential carriers of COVID-19.

It appears that the most important measure airlines can take to prevent the spread of COVID-19 during flights is to require passengers and crew wear face masks.

There is little doubt that every health safety measure the airlines take will improve the likelihood that air travelers will remain uninfected by COVID-19. Keeping passengers at least 15 inches apart for most of their flight can somewhat improve their safety. Sooner or later, however, all the airlines will have to start filling their planes to capacity, as flying at or below 60 percent capacity isn’t sustainable for any airline. At that load factor they are losing money on every flight.

It appears that along with cleaning, disinfecting and maintaining HEPA air filtration on aircraft, the most important safety measure airlines must maintain is a mandatory face mask requirement. More than any other measure available to airlines, face masks have the best potential for keeping respiratory droplets from infected passengers out of the air breathed by the other passengers and flight crew during each flight.