Airlines and airports around the world are doing everything they can to instill confidence that it is safe to fly again, despite the coronavirus pandemic.

Airlines are requiring face masks for passengers and staff, imposing new aircraft cleaning procedures, using social distancing to board flights, blocking middle seats on planes and, in one case, even prohibiting passengers from lining up to use plane bathrooms.

As to the airports, they are screening passengers’ temperatures through high- and low-tech means; using biometric screening to speed check-in, security and customs and immigration processes; and using autonomous robots to clean terminal floors.

But none of it is consistent. And it’s unclear whether the measures are enough.

Will social distancing measures work, for instance, when travelers are sitting on planes for hours with strangers? Temperature checks may identify those already ill, but how do you screen for the virus when, by some estimates, 35% of people with it are asymptomatic and 40% of transmission occurs before people feel sick?

“So much is uncertain right now,” said Henry Harteveldt, founder of Atmosphere Research Group, a San Francisco travel analysis firm. “Do airports and airlines need to invest in something long term that will be permanent, like airport security, or are these short-term, tactical responses?”

“This uncertainty, combined with unnecessary variation from airport to airport in health screening processes, ends up with confused consumers not being confident enough to take a trip,” Harteveldt said. “They will travel only when it’s necessary, rather than when they want to, whether it’s for business or pleasure.”

The International Air Transport Association, the trade group for the global airline industry, laid out what it called a “road map” for restarting aviation last month. It recommended “layered” measures that would be “globally implemented and mutually recognized by governments.” These included preflight passenger contact tracing; temperature screening as travelers arrived at airports; use of masks by passengers; masks and personal protective equipment for airline and airport staff; self-service, touchless options for check-in and baggage drop-off; and electronically processed customs procedures.

But it rejected some airlines’ policy of blocking off airplanes’ middle seats because, it said, “the risk of transmission of COVID-19 from one passenger to another passenger on board is very low.”

And while the air transport association may have hoped its guidelines would reassure travelers, Timothy O’Neil-Dunne, a multimillion-mile frequent flyer and a principal of 777 Partners, an investment firm, said they ignored the “critical question that has to be answered: How can I be assured only nonspreaders of COVID-19 will be allowed on the aircraft with me?”

The only way to be certain, he said, “is to test in the nasal cavity for the virus.”

Further, Robert Crandall, a former president and chairman of American Airlines, called the association’s suggestion that onboard infection is unlikely “nonsense, since atmospheric inhalation is the primary means of transmission.”

One policy widely required by airlines is the use of masks or facial coverings by passengers and staff.

At some carriers — including Qatar Airways, Philippines Airlines and AirAsia — flight attendants are wearing what are essentially hazmat suits.

American, United and Southwest Airlines, among others, have enhanced their aircraft cleaning programs, while most modern aircraft use HEPA (high-efficiency particulate air) filters, also used in hospital operating rooms, that extract virtually all microbes and viruses from cabin air. Still, there’s no proof the filters can fully protect travelers from the coronavirus.

The transport association’s guidelines notwithstanding, some carriers — particularly those in the United States and Europe — are leaving middle seats on flights empty for the time being, to enforce social distancing. United, however, got a black eye last month, when a transcontinental flight was jammed with passengers. The airline later said it would adjust “seat selection to avoid seating you next to other travelers.”

In a call with investors last week, Scott Kirby, United’s former president and new chief executive, said, “You can’t be 6 feet apart on an airplane, middle seat or not,” adding later, “What makes an airplane safe is HEPA air filters recirculating the air every two to three minutes, wearing a mask on board the airplane, cleaning the airplane.”

Ryanair, the low-cost, Dublin-based carrier, which plans to resume 40% of its regular service on July 1, opposes blocking middle seats. It has also established one of the most unusual new policies: It plans to prohibit “queuing for toilets” during flights, though “toilet access will be made available to individual passengers upon request.”

Delta Air Lines is not only requiring face masks, but it is also sanitizing check-in kiosks and counters, baggage stations and security station bins at airports, as well as disinfecting gate areas, jet bridges and employee areas.

In addition, it is sanitizing aircraft lavatories, overhead bin handles, tray tables and seat-back screens before every flight. It is also temporarily blocking middle seats; cutting back food and beverage offerings to “reduce service touchpoints”; and replacing HEPA filters twice as often as recommended by the manufacturer.

Frontier, Air France and Singapore Airlines, among others, are performing temperature checks of passengers. Etihad is doing a trial with volunteers at Abu Dhabi International Airport of a contactless, self-service kiosk to measure temperature, heart and respiratory rate.

Incheon International Airport in Seoul, South Korea, disinfects its halls and does fever checks in multiple locations. London Heathrow is doing a trial of thermal screening technology to detect arriving passengers’ elevated temperatures, while the Vienna airport is offering a coronavirus test, at $211, to both arriving and departing passengers.

Airports are also dealing with quarantine policies, established by local and national governments, that can be inconsistent or mishandled. When Americans returned from overseas in March, they often faced hourslong waits, with no social distancing, in airport customs lines, as well as conflicting or no guidance on quarantining. Travelers going to some, though not all, states — including Alaska, Hawaii, Nevada and New Mexico — are subject to 14-day quarantines. The British government plans to impose on June 8 a 14-day, self-quarantine requirement for most arriving travelers.

Both Cincinnati/Northern Kentucky International Airport and Dallas-Fort Worth International Airport will soon use employees to test a screener that combines an infrared camera and artificial intelligence to read their temperature.

Pittsburgh International Airport has a robot, with a brain designed by Carnegie Robotics, that uses ultraviolet light to clean floors. The airport is also considering using the light to sterilize elevator buttons and the handrails on escalators and people movers. The Cincinnati airport recently started using an Avidbots NEO robot, widely used at overseas airports, to clean its floors. Brian Cobb, the airport’s chief innovation officer, said it planned to use data provided by the robot to monitor and, if necessary, redirect travelers, to maintain social distancing.

The Dallas airport is using lights and digital displays to indicate free restroom stalls. Hartsfield-Jackson Atlanta International Airport is installing 400 new hand sanitizers that employ a smart monitoring system.

Miami International Airport is using a new service, from the software developer Iinside, that monitors and evaluates social distancing on security lines. Tampa International Airport has installed plastic shields in high-traffic areas and social distancing markers and signs. It has also reduced seating, and increased and upgraded cleaning efforts. It is advising travelers to arrive at least two hours before departure “to help prevent crowding caused by last-minute rushing.”

Two technology companies, SITA and Collins Aerospace, are promoting touchless initiatives for airports that use biometric facial recognition and mobile technologies for check-in, baggage drop-off, security screening and boarding.

The use of biometric screening continues to be debated, at least in the United States and Europe. Although O’Neil-Dunne and Harteveldt support the screening, Harteveldt suggested that whoever uses the technology must operate “at the highest level of data security” to insure passengers’ health information is kept secure.

O’Neil-Dunne said passengers might have to be more flexible about privacy, to protect their own and others’ health.

“Ethics are fine when ethics are all that matters,” he said. “In this case, it’s a pandemic virus. You’re not just dealing with individual rights, you’re dealing with fellow passengers’ basic human rights, and I think that has precedence.”

There are other options. Sheldon Jacobson, a professor of computer science at the University of Illinois in Urbana who helped design the Transportation Security Administration’s PreCheck program — which provides expedited security screening at U.S. airports to low-risk travelers — suggested an automated, biometric identification system for PreCheck-vetted passengers. To reduce interactions between agents and travelers, he also suggested that the TSA direct certain passengers into PreCheck lines, adding new lines, if necessary, to enforce social distancing.

Dr. Joshua Schiffer, an infectious disease physician at the Fred Hutchinson Cancer Research Center in Seattle, said, “It’s next to impossible to have complete confidence you won’t get infected” on flights. But he said he hoped that airlines would provide travelers “publicly available information on what the projected risk would be to a certain destination, so you could choose your airline based on the quality of this information.”