Would you “scam” an airline’s ticketing policy if it saved $25? $70? $400?

A federal lawsuit is bringing public attention to “hidden city” ticketing, the technique of buying an airline ticket between two cities with a connection but ditching the rest of the trip. Say, for example, you want to fly from Boston to San Francisco but notice that a ticket from Boston to Seattle — with a connection in San Francisco — is cheaper. Once your flight lands in San Francisco, you prance out of the airport at your intended destination, pocketing the savings.

Airlines hate this maneuver — which has been around for decades — and argue that it violates tickets’ terms of sale. Others contend that it’s no big deal.

“I think it’s fair game,” said John DiScala, a travel expert who blogs as Johnny Jet. “I think it’s smart for the consumer.”

Jay Sorensen, a consultant and former executive with Midwest Airlines, argues that airlines also violate the terms of sale with their customers “and then rely on the customer to write a letter to complain to get that violation addressed.” (In a phone call Tuesday, Sorensen noted that his wife, who also is a former airline executive, vehemently disagreed.)

“I think there are greater sins in life,” he said.

United, the world’s second-largest airline, along with online travel agency Orbitz Worldwide, are not convinced. They have filed suit seeking an injunction to stop a New York programmer’s Web site, Skiplagged.com, from sending United ticket buyers to Orbitz.com to buy such “hidden city” tickets.

The ticketing technique “interferes with United’s ability to sell unused seats on the final leg(s) of connecting flights, resulting in the loss of revenue that United would have earned by selling the unused seats,” the company said in its lawsuit last month in U.S. District Court in Chicago. The companies also are seeking at least $75,000 in damages and attorney fees.

“This practice violates our fare rules, and we are taking action to stop it to help protect the vast majority of customers who buy legitimate tickets,” said Christen David, a spokeswoman for United.