Southwest Airlines (LUV 2.08%) CEO Gary Kelly announced on Thursday that the company would begin selling middle seats again beginning Dec. 1. The company, along with a handful of other airlines, had blocked sales of certain seats in order to promote social distancing due to the pandemic and slow the spread of the coronavirus during air travel.

"This practice of effectively keeping middle seats open bridged us from the early days of the pandemic, when we had little knowledge about the behavior of the virus, to now," Kelly said. "Today, aligned with science-based findings from trusted medical and aviation organizations, we will resume selling all available seats for travel beginning Dec. 1, 2020." 

A person wearing a mask spraying aerosol disinfectant on a plane.

Airline deep-cleaning methods are effective at killing the coronavirus, studies have shown. Image source: Boeing.

Recent research seems to support Southwest's view.

In a study commissioned by Boeing (BA -0.87%), researchers from the University of Arizona sprayed a live, surrogate virus on strategic high-touch areas of an unoccupied plane. The substitute, MS2, is safe for humans but is more difficult to kill than SARS-CoV-2, the virus that causes COVID-19. They then used the normal deep-cleaning and disinfecting methods employed by airlines since the onset of the pandemic. The researchers then analyzed each of the areas post-cleaning to determine how effective the methods were and found that the virus had been successfully eradicated. 

There were also promising findings in a study released by the Department of Defense. Researchers there used fluorescent tracer aerosols to represent airborne particles produced by exhaling and coughing. They found that the combination of HEPA filters, high air exchange rates, and the recirculation of air on modern jets reduced the risk of aerosol dispersion (transmission of the virus through the air) by 99.7%. 

Researchers in Hong Kong came to a similar conclusion. Across five Emirates airlines flights in June and July, 58 passengers were found to have been infected with the coronavirus before their flights, but none of the nearly 2,000 other passengers on the flights with them contracted the disease.