United CEO Oscar Munoz's latest apology was to Congress.

The United Airlines boss was called before a hearing of the House Transportation committee Tuesday over the violent removal of an airplane passenger and the bungled apology that followed.

Munoz began with another apology for the incident on April 9 in which a United (UAL) passenger was dragged off an overbooked flight in Chicago. The airline settled out of court with the passenger, Dr. David Dao.

"We had a horrible failure three weeks ago. It is not who we are," Munoz said. "We will do better."

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Munoz said an investigation into the incident by the airline found four basic failures. First, it should not have had police remove a passenger who was not a safety threat. Second, it shouldn't have created a seat shortage by booking crews that needed to travel on the flight at the last minute. He also said that United didn't offer enough money to motivate passengers to voluntarily give up their seats.

"Our employees did not have the authority to do what was right or use common sense," Munoz said. "This has to be a turning point for 87,000 professionals here at United."

Munoz was one of five airline executives appearing before a hearing of the House Transportation Committee on Capitol Hill. The others were United President Scott Kirby as well as lower-level executives from American Airlines (AAL), Southwest (LUV) and Alaska (ALK). An aviation consultant from Consumers Union testified.

Related: United settles with passenger who was dragged off plane

Both the committee's top Republican and Democrat both decried the state of air travel for customers. Both told the executives they need to improve or face action by Congress.

"Congress will not hesitate to act when your customers, our constituents. are not treated the way they deserve," said committee chairman Bill Shuster.

Many committee members from both parties voiced frustration with their own flying experiences.

While much of the discussion during the hearing focused on overbooking and passengers getting bumped off flights, there were also complaints about airline industry consolidation and the lack of passenger choices, fees, and even seat size.

"We're kind of sick of it as the consuming Americans," said Rep. Michael Capuano, a Massachusetts Democrat. "We've got to fly. You've got us. If you want to keep treating us this way, fine. I guess we can only do so much. But there will come a day when Congress won't accept it any more on behalf of the American people."

William McGee, speaking for Consumers Union, suggested that no passenger should ever be bumped involuntarily.

Related: 10 things United is doing to avoid another dust-up, drag-out passenger fiasco

"We are not aware of other industries in America where the business is given this kind of free license to oversell the product, with so little accountability for failing to deliver," McGee said. "The needed change is that all denied boardings should truly be voluntary. The airline should pay whatever compensation is necessary to convince a passenger to willingly give up the seat."

Southwest announced last week that it would no longer overbook flights. Rep. Peter DeFazio, the leading Democrat on the committee, urged the other airlines to follow Southwest's new policy.

"Southwest, are you going to go broke,[now that] you're not going to overbook any more?" he asked the Southwest executive sarcastically.

"We are not going to go broke," replied Bob Jordan, the Southwest executive vice president who appeared at the hearing.