– Federal lawmakers, including Minnesota’s U.S. senators, are pushing United Airlines to better explain its forced removal of a man from a plane after viral videos of the incident sparked an uproar over protections for passengers on overbooked flights.

“Air travel has gotten more and more difficult, and people have to keep some sense of dignity when they’re paying to be on a plane,” Sen. Amy Klobuchar, D-Minn., said Wednesday in an interview.

Klobuchar, a member of the Senate Commerce Committee, called for the panel to hold a hearing “to examine current airline passenger protections and needed improvements.” Also this week, the committee’s Republican and Democratic leaders sent letters to United demanding that the airline provide a “full accounting of the incident” by April 20.

Over the weekend, passengers on a full flight headed from Chicago to Louisville, Ky., were asked to give up seats to make way for four airline employees. It’s routine for airlines to overbook flights and count on a few people not to show up, in order to maximize profits and avoid wasting empty seats. When David Dao refused the chance to take a later flight and $1,000, authorities grabbed him out of his seat as he screamed, and pulled him down the aisle. Dao, a doctor, is being treated for injuries.

United CEO Oscar Munoz told ABC News in an interview Wednesday that such an incident “can never, will never, happen again on a United Airlines flight.” He said he felt ashamed by what happened.

Klobuchar, who also sits on the Commerce Subcommittee on Aviation Operations, Safety and Security, said she believes airlines must have discretion to remove passengers who are drunk or threatening. But she said a Commerce Committee hearing would be a chance to explore the rules airlines use to remove passengers from planes for reasons other than safety — including standards for bumping passengers in order to seat airline employees.

Klobuchar’s fellow Minnesota Democrat, Sen. Al Franken, also raised questions about the incident. He and Klobuchar were among 20 Democratic senators who wrote in a letter to Munoz that overselling tickets can have “severe consequences” for travelers.

“At a time when the airline industry is earning record profits, it is our hope that the industry can make great strides to improve customer service and implement best practices,” the senators wrote.

Lawmakers questioned how many times United removed ­passengers — forcibly and otherwise — due to overbooking, and what the company’s standard procedure is for doing so. Additionally, they asked why the airline didn’t offer $1,350, the federal cap on compensation for involuntarily denied passengers, before requiring their removal.

Last year, 40,000 people on domestic airlines were involuntarily bumped from a flight, at a rate of 0.62 out of every 10,000 passengers, according to a recent report from the U.S. Department of Transportation.

United involuntarily bumped 3,765 travelers in 2016, at a rate of 0.43 out of every 10,000 passengers. Those figures put United roughly in the middle of the dozen airlines the Department of Transportation included in its report. ExpressJet, Southwest, and SkyWest airlines bumped the highest rate of passengers, while Hawaiian, Delta and Virgin airlines bumped the lowest.

Sen. Chris Van Hollen, D-Md., said he would introduce legislation preventing airlines from forcing out passengers who have already boarded a plane. Instead, airlines would have to offer enough compensation for people to leave voluntarily.

Klobuchar said she expects to talk about the matter soon with Sen. John Thune, R-S.D., chairman of the Commerce Committee. Klobuchar helped push an “airline passenger bill of rights” that took effect in 2012, banning lengthy tarmac delays and doubling compensation for passengers involuntarily bumped from flights.

Klobuchar said it’s possible that lawmakers could look at adding to those rules, but she wasn’t ready to call for any yet. “We have to get a sense of the more global environment,” Klobuchar said.