American Airlines touts a new tool to combat COVID. But does it really make flying safer?

Our mission to help you navigate the new normal is fueled by subscribers. To enjoy unlimited access to our journalism, subscribe today.

American Airlines announced federal approval of a new disinfectant that the airline says it will use on some flights to improve protection against surface transmission of the coronavirus. The product will be integrated into what American calls its Clean Commitment, an effort to keep its planes safe enough to draw back travelers.

But the evolving science on COVID-19 points to ongoing uncertainty about whether it’s safe to fly—and about the airline industry’s broader prospects.

The new approval by the U.S. Environmental Protection Agency is for a product called SurfaceWise2, produced by Dallas-based Allied BioScience. The disinfectant will be applied using electrostatic sprayers, which add an electromagnetic charge to particles of cleaner, making them better adhere to surfaces. Electrostatic disinfectant spraying is already widely used by airlines, including American competitors Southwest and Delta.

The key difference is that SurfaceWise2 is effective for up to a week with a single application. That may be as much of a boon to labor efficiency as safety. Existing disinfectant sprays are similarly effective, but are applied by airline staff after every flight.

Founded in 2005 and privately held, Texas-based Allied secured a large new investment in April premised on its work on anti-COVID products. According to Allied, the new EPA approval makes SurfaceWise2 the only coating approved for long-term continuous disinfection of COVID-19. Its effectiveness has also been supported in independent lab tests.

But the EPA approval, issued on an emergency exemption basis, is quite limited. For one year, the product can be used by American Airlines flights that pass through airports in Texas, and by two physical therapy clinics operated in Texas by Total Orthopedics Sports & Spine. Speaking to the press today, EPA chief Andrew Wheeler said other entities that want to use the product may apply separately for an emergency exemption via their state authorities. Allied BioScience told CNBC it will pursue broader approval that would make its disinfectant more easily available.

More effective disinfection on planes should reduce the transmission of coronavirus via surfaces, such as armrests, where virus left behind by an infected person can stay alive for hours. The World Health Organization warns that COVID-19 can cause an infection if it’s carried from surfaces to the eyes, nose, or mouth.

The bigger risk: The air you breathe

Better surface disinfection, however, increasingly pales next to worries about air quality on passenger flights. There is now strong scientific consensus that COVID-19 is primarily spread by direct social contact, with surface transmission playing a smaller role. And there is increasing evidence that micro-droplets exhaled by infected individuals can remain airborne and infectious for hours.

That is particularly worrying in the case of airliners, in which many passengers are confined in a small space. Restaurants, offices, and other businesses have been severely curtailed during the pandemic because gathering people in closed spaces increases the risk of infection.

Despite appearances, most airliners are considerably safer than eating indoors in a restaurant. American says that on all planes in its fleet, air is either replaced with outside air, or scrubbed using hospital-grade HEPA filtration, every two-to-four minutes. That’s nearly twice the average replacement rate in an office building. Additionally, air is recycled only within horizontal ‘zones,’ reducing spread along the length of a plane. American says these features have been standard since the late 1990s.

Nonetheless, there is clear evidence of airborne transmission risk on passenger flights. A 2003 study of the transmission of the SARS coronavirus on a passenger plane found that a single symptomatic person spread the virus throughout the cabin of the plane, infecting as many as 22 others. More recently, a study of COVID-19 transmission on a March 2020 international flight found possible transmission at a distance of up to two rows.

All major U.S. carriers now require masks, which reduce the distance exhalations spread. But American has rolled back one of the most significant measures to control the spread of COVID: since July 1, it has not blocked off seats to maintain greater social distancing during flights. United and Spirit airlines have also rolled back those policies, despite evidence that they are very effective at reducing transmission risk. Delta and Southwest, by contrast, have said they will continue blocking seats until at least the end of September.

Continued uncertainty about safety has become an existential threat for individual airlines, and is expected to upend the airline industry as we know it. S&P Global has estimated air travel demand will be down 55{ce8ce7cc98bffdc4302011057a79600ea02c464c5536f1477c12acdb8bd79c00} for 2020, and won’t recover until 2024.

Those declines have triggered huge cuts across the industry. One running tally lists more than 20 airline bankruptcies globally so far this year. And major U.S. carriers have been forced to reduce service. Last week, American announced it will cut service to 15 U.S. cities, and has signaled that more cuts could be coming.

More must-read tech coverage from Fortune:

• ‘It’s clicks versus bricks’: Why tech stocks won’t be fading anytime soon
• Samsung Note20 Ultra review: Why this big phone works for the COVID era
• Facebook and NYU researchers discover a way to speed up MRI scans
• The U.S. Postal Service is seeking a patent for voting by phone
• Electric-vehicle startup Canoo to go public, joining the wave of companies chasing Tesla’s success