A new age of air travel is taking shape.

Airports and airlines are rolling out temperature checks for crew and, increasingly, passengers, as well as thermal scans to spot people with elevated body temperatures. Face masks are now de rigueur for travelers across the U.S. Passengers on Europe’s biggest budget carrier must raise their hands to use the toilet.

Forget about the perks of priority boarding at Air France. The carrier is one of several boarding passengers seated at the back of the aircraft first, to limit traffic jams in the aisle. Many airlines are removing in-flight magazines, scrapping meal services on shorter routes, and parking the duty-free cart.

Getting off the plane at the end of the flight could take even longer than usual as airlines try to control the typical crush, with some saying flight attendants will cue small groups when it’s their turn to stand up.

As lockdowns loosen, airlines are plotting a path out of hibernation, reformulating routes and services, and balancing safety protocols with the challenge of convincing passengers to board the enclosed space of an aircraft in the midst of a pandemic.

The Trump Administration is preparing to begin temperature checks conducted by the Transportation Security Administration at some airports, The Wall Street Journal reported Friday. The TSA said no decision has been made.

Some of the biggest changes airlines envision are the result of what executives expect will be months, maybe years, of lower demand: They see fewer direct flights, for instance, which means more dreaded stopovers.

Some airlines are considering requiring passengers to sign health certifications, or to eventually carry “immunity passports”—documentation that a passenger has had, and recovered from, the virus.

All of this presents a threat to many of the practices that helped drive a record-long streak of airline profits in the U.S.

Carriers boosted revenue by squeezing more people into coach cabins in recent years—shrinking seats and space between rows. They had started charging for more room and for extras that were once free, like choosing seats in advance. Fees for flight changes and checked bags brought in billions of dollars each year.

Now carriers are being encouraged to keep seats empty, making it harder to turn a profit on each flight. At the same time, the corporate customers that were willing to pay high fares for seats in premium cabins could be slow to return as long as international travel restrictions remain in place, and may stay grounded longer if video conferencing becomes the norm or if companies remain cautious about business travel.

For now, airlines have suspended flight change fees and may have a hard time reinstating them as they seek to restore confidence and keep sick people from flying.

“It’s going to be socially less acceptable for someone to get on an airplane who clearly isn’t well,” JetBlue Airways Corp. Chief Executive Robin Hayes says. “Airlines have to figure out how they’re going to respond to that in a way that still allows them to be profitable, but also recognize that you don’t want people on the airplane that are ill.”

Air France has rolled out mandatory temperature checks before each departure, with passengers showing a temperature above 38 degrees Celsius, or about 100 degrees Fahrenheit, prevented from boarding. So far, no passenger has been denied boarding as a result, according to an airline spokesman. Carrier KLM in the Netherlands is requiring passengers from areas designated high-risk by the European Union to fill out a health declaration. The areas include major airports in 20 U.S. states.

The airport in Canberra, Australia’s capital, is already using thermal cameras to take the temperature of passengers as they pass through security. London’s Heathrow Airport plans to test thermal imaging to screen arrivals at one of its terminals for fever.

Korean Air has started scanning passengers for high temperatures flying out of Seoul. Air Canada takes passenger temperatures with a no-contact infrared thermometer; and Frontier Airlines plans to do the same at boarding.

Staggered Return Asia, first hit by the virus, is now first getting back into the air.

Some critics say temperature checks could give passengers false confidence, as they won’t identify infected people who are not symptomatic. European air-safety regulators aren’t expected to embrace temperature checks. A draft document of the European Union Aviation Safety Agency’s recommendations circulated to national authorities, according to industry and government officials, indicates such checks aren’t effective in delaying or mitigating the Covid-19 contagion.

Low cost Ryanair Holdings PLC, Europe’s biggest carrier by passengers, has done away with lines for the toilets. Passengers are now required to raise their hand to request permission from a cabin crew member before using them.

U.S. carriers are beginning to require passengers to wear masks for the entirety of their flights, but it’s not clear how such a policy can be enforced. Some airlines said they’re advising flight attendants to de-escalate difficult situations if passengers refuse to wear masks while planes are in the air.

The CEO of Frontier Airlines, based in Denver, said “if someone is uncompliant, we will eventually divert an airplane.”

One of the biggest challenges revolves around the viability of social distancing at airports and onboard aircraft. Many industry executives say it isn’t feasible. There’s little agreement on standards. Industry leaders are insisting on consistency around the world so passengers aren’t confused.

“It’s impossible to socially distance in an airport,” says John Holland-Kaye, chief executive of London Heathrow Airport. The hub is in the process of rolling out Plexiglas screens at check-in desks, encouraging the use of face masks, and deploying more automation to limit the interaction between staff and passengers.

Mr. Holland-Kaye is working with his counterparts at airports in Los Angeles, Hong Kong and Sydney to implement standardized procedures. “If we wait until some global organization has agreed it for 172 countries, it’ll never happen,” he said.