NEW YORK >> Move over, on-time performance. The new key standard for airlines and passengers is: “How clean is it?”

The airlines are busily fine-tuning their cleaning procedures — where they clean, how frequently and with which tools. To get a sense of what’s changed, I recently witnessed the disinfection and cleaning process performed from start to finish onboard a Delta Air Lines jet at Kennedy International Airport in New York.

In short, it was meticulous — enough to delight even a hardened germophobe.

Here’s what passengers need to know about how an airplane gets disinfected and cleaned between flights.

Question: How was the plane cleaned?

Answer: Passengers disembarked from a 76-seat Republic Airways regional jet that had arrived at Kennedy Airport from Boston. Republic operates the plane on behalf of Delta. A crew of nine cleaners made quick and efficient work of the airplane.

First, a worker passed through the cabin to open the overhead bins and each tray table on the aircraft. The window shades were opened halfway, which allows for disinfectant to stick to both the window and the shade.

Next, a single worker passed through, equipped with a backpack filled with disinfectant and a spray nozzle that looked like a Super Soaker water gun, called an electrostatic sprayer. (More about that, later.) He sprayed a fine mist, slowly moving from the lavatories at the back of the cabin to the front. For his protection, the worker wore a plastic face shield and a face mask. Every passenger seat, side wall, overhead air vent and bin were fogged with a fine mist. It took about 10 minutes from tip to tail.

The rest of the cleaning crew waited on the air bridge while the plane was fogged, wearing face masks. Once fogging was completed, the cleaners boarded and got to work. One was charged with scrubbing the forward galley and two were sent to the rear lavatory. The rest of the crew began wiping down the seats, seat backs, tray tables, armrests and sides of the seats, using hand-held spray bottles filled with the same disinfectant as was used in the fogger. One cleaner wiped down the inside of the overhead bins.

At the rear of the plane, the lavatory was wiped down several times with disinfectant-soaked wipes — similar to heavily soaked Lysol wipes.

The regional jet had very little in the way of passenger garbage as there is no onboard food and drink service offered on short flights like this one. I saw one water bottle left behind in a seat pocket.

If needed, the floors are vacuumed. (This one wasn’t.) If a plane sits for longer than eight hours — typically a long-haul jet — then the airline will perform a deep clean, a member of the Delta operations team explained. During a deep clean, every seat cushion is removed, the seats are vacuumed and the carpet is shampooed throughout the cabin.

Q: How frequently are aircraft cleaned or disinfected?

A: It varies by airline, but planes are being cleaned more frequently now than before the pandemic. Delta, American, United and Southwest all use electrostatic sprayers with differing frequency.

Commercial aircraft generally fly either short to medium distances many times per day, such as New York to Boston and back, or long-haul flights less frequently, such as New York to Los Angeles or overseas. The time between landing and departing is called a “turn.” In Delta’s case, regional aircraft are on the ground for about 90 minutes, and larger aircraft for about two hours. Other airlines, such as Spirit and Frontier, have much quicker turns.

In Delta’s case, every aircraft is disinfected and cleaned after each flight, according to the airline. The process takes about 15 minutes, carved out from the time the plane was already on the ground.

“We’re talking about a few more minutes added to the schedule,” said Stephanie Baldwin, Delta’s vice president of airport operations at Kennedy. A larger aircraft takes more time and more hands; I boarded a freshly cleaned Boeing 767 that had arrived from Los Angeles. It had been cleaned by about a dozen workers, similar to how the Republic Airways regional jet was cleaned.

A spokesman for United Airlines wrote in an email that the airline was deploying electrostatic spraying before “most flights.” Southwest Airlines wrote in an email that their aircraft are deep cleaned for six to seven hours every night.

Similarly, American Airlines wrote in an email that the airline is “disinfecting high-touch surfaces at every turn with a solution similar to what some competitors use when electrostatically spraying the inside of aircraft.” In addition, American said it is performing electrostatic fogging with a disinfectant the airline claims provides seven days of protection against COVID-19. (The airline declined to disclose the name of the disinfectant.)

A spokesman for JetBlue wrote in an email that the airline performs electrostatic spraying on longer turns or when the plane sits overnight. In addition, the airline announced last Wednesday a pilot program with Honeywell to test an ultraviolet light system that sweeps the cabin in about 10 minutes without the use of chemical disinfectants.

Q: What chemicals are used to disinfect the plane?

A: Delta’s disinfectant of choice is called Matrix 3, which is approved by the Federal Aviation Administration for use on airplanes since it does not corrode aluminum. It’s a mix of ethanol and Tetrasodium EDTA, a commonly used disinfectant. I did not detect a strong smell. Matrix 3 is more powerful than common household cleaners and is rated by the Environmental Protection Agency as able to kill a harder-to-kill pathogen than that which causes COVID-19.

Q: What is fogging and how does it work?

A: Fogging is a common term for electrostatic spraying. The technique has been used for decades to paint automobiles and in agricultural spraying. However, applying disinfectant with electrostatic sprayers is relatively new; NYU Langone Medical Center said it began using the technology in 2018, for example.

Unlike with a spray bottle, the nozzle imparts a positive charge to droplets of disinfectant, each 85 microns in size — roughly the thickness of an average human hair. The electrical charge causes the individual droplets to repel against each other and spread out over a wide area. Simultaneously, the droplets are attracted to negatively (or neutrally) charged nonporous surfaces — such as an airplane seat or side walls.

“It’s a little bit like rubbing a balloon on your hair, then sticking the balloon to the wall. Every single molecule leaving that nozzle is charged. They are attracted to surfaces like a magnet,” said Joshua Robertson, the chief executive of EMist, a Texas company that manufactures electrostatic sprayers for United Airlines and Alaska. A competitor supplies Delta Air Lines.

Q: Why is fogging effective?

A: The charged disinfectant molecules get everywhere that a spray bottle and rag cannot. “It’s a comprehensive coat,” Robertson said. “Electrostatic spraying simplifies the disinfecting process and mitigates human error. It gives the workers better tools to do their job better and lets the chemical do its job.”

Said Robertson: “We’ve been applying disinfectant for over a hundred years, dunking a cloth in solution and wiping. This is the 21st-century equivalent with better chemicals, applied faster and more efficiently.”

Q: Does the fogging leave a residue?

A: At first, yes. But within two minutes of dwell time — the time the chemical sits on a surface undisturbed — the disinfectant had mostly dried. (Read the instructions for a household cleaner such as Clorox or Lysol; you’re advised to let it sit for at least a few minutes.) Delta built in dwell time when cleaning aircraft. The little residue that rested on the surfaces was subsequently wiped down by the cleaning crew. By the time you board, the disinfectant will have dried — and killed 99.9999% of any pathogens.

Q: Why didn’t the airlines do this kind of deep clean before COVID-19?

A: Airlines did not comprehensively disinfect and clean aircraft between flights as they do now. Tray tables and seats were cleaned after long-haul flights but not typically between turns on short flights.

Airlines emphasized on-time performance and cost management in a bid to offer lower fares. Disinfecting and cleaning costs include FAA-approved disinfectants, contract labor, additional time on the ground — and now specialized equipment.

Q: How do airlines keep track of which aircraft have been cleaned?

A: After each turn, the Delta cleaning crew chief confirms that the aircraft has been cleaned to the airline’s standards. This information is fed to a central database. (Delta passengers even get a mobile app notification that their plane has been disinfected and cleaned.) The work is audited by lead gate agents, who perform some 48 audits per day, 24 of which relate to cleanliness, said James Whitelaw, director of airport operations for Delta at Kennedy. “Post-flight passenger surveys allow Delta to compare passenger feedback on flight cleanliness with operations team signoff. This feedback loop provides for accountability,” he said.

Passengers have expressed to Delta that onboard cleanliness is a differentiator, Whitelaw said.

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