Airlines have come up with yet another way to charge passengers: pay cash to cut the line.

In addition to charging for checked bags, unchecked bags, extra legroom and priority boarding, many airlines are now marketing a private tech company that uses fingerprints and iris scans to verify a traveler’s identity at security checks, allowing them to bypass TSA lines.

“It’s extortion,” said Amy Zavatto, a Staten Island-based food and spirits writer who stood on a long line to pass through security at La Guardia Airport last week.

As she queued up for her Delta flight to Rochester, she said, she was approached by an agent who encouraged her to sign up for Clear, the company that provides biometric screening at airports and other venues.

“I’m … wondering if I’m going to make my flight, when along comes an agent who coos to me and the people behind me on line that if we sign up for Clear, it’ll just take a few short minutes and some fingerprinting and then we’ll get to go all the way to the front of the line,” Zavatto told The Post.

Zavatto said a handful of passengers signed up on the spot for the service, which carries a $179 annual price tag, although some airlines offer a discount to their frequent flier customers.

Zavatto said she refused the perk and languished on line while those who signed up were immediately ushered to the front.

“It wreaks of silky scamminess,” she said about being approached on the TSA security line while desperate to make her morning flight.

A spokesman for Clear admitted that the company targets passengers on long queues before their flights. Clear operates at 31 airports across the country, including JFK and LaGuardia. It is also available at sports venues, including Yankee Stadium, Citi Field and Madison Square Garden, where it provides faster lines with “expedited entry,” and some Hertz car rental locations.

“Our ambassadors are there to assist our members, but they are also there to explain the benefits of membership to non-members, which include verifying their identity with a tap of their finger or blink of their eye so they can get through security and on their way faster, without sacrificing security,” the spokesman said.

“Clear is taking advantage of people who are in long lines,” said Douglas Kidd, executive director of the National Association of Airline Passengers, a passenger advocacy organization based in Virginia.

Kidd said that passengers who sign up with Clear still must go through security pat downs and a body scanner. They still have to remove their shoes, he said.

“It’s just another way for airlines to charge you more,” he said, adding that TSA’s PreCheck, which costs $85 for five years, is a better option for expedited security checks.

But airlines are backing Clear, and encouraging passengers to use the service through their frequent flier programs. Delta Airlines has a 7 percent equity in Clear, and United Airlines recently said that it would also take out equity in the technology company. Delta SkyMiles members pay between $109 and $119 for the service, and elite Diamond Medallion members receive it for free.

Clear plans to launch its service at Newark Liberty Airport later this summer, the spokesman said.