Politicians have raised the threat of tougher rules on US airlines as they grilled industry executives at a hearing in Washington.
United Airlines chief Oscar Munoz apologised again for the forced removal of a passenger last month.
It was one of a series of incidents that has prompted dissatisfaction with US airlines to boil over.
Mr Munoz and other airline executives promised improvements for passengers at the hearing on Tuesday.
"Seize this opportunity because if you don't, we're going to come, and you're not going to like it," said Rep. Bill Shuster, the Pennsylvania Republican who heads the committee that hosted the hearing.
Mr Shuster said that although he did not believe in over-regulating businesses, Congress would "not hesitate to act" to improve conditions for customers.
United has apologised after staff called law enforcement to forcibly remove passenger David Dao from a flight on 9 April to make room for crew members.
The airline has settled a lawsuit and announced policy changes, including boosting the amount of money staff can offer passengers to take a different flight.
"We had a horrible failure three weeks ago," Mr Munoz said on Tuesday. "It is not who we are. It is not this company and it is not ... this industry."
Airlines in the US have come under pressure, as complaints over new fees for baggage and other items, smaller seats, tarmac delays, cancelled flights and overbooking have gotten louder.
Recent incidents, captured by passengers on their cell phones and shared widely on social media, have heightened the issue.
American Airlines also suspended an employee after a clash with a passenger over a baby pram.
A landmark law in 1978 de-regulated US airlines. It is credited with ushering in lower fares and allowing low-cost carriers to emerge.
Tighter rules would be a surprise in a Congress dominated by Republicans, who typically favour a market-oriented approach and lighter rules for industry.
Leave it to the airlines?
Earlier this year, US President Donald Trump proposed privatising air traffic control operations, which are currently handled by the Federal Aviation Administration. The move is backed by most airlines.
Several members of the committee said they hoped the industry would police itself.
But some members, including Republicans, raised the need for stricter oversight, citing industry consolidation, cumbersome fees and falling fuel costs they said had not been transferred to passengers in the form of lower fares.
The Transportation Department on Tuesday issued a report that the U.S. airline industry made $13.5 billion in net profits in 2016.
Author William McGee, who represented the Consumers Union at Tuesday's hearing, noted a report in The Economist that found profits per passenger in North America were more than $22, nearly three times higher than in Europe.
"What we cannot do is continue to leave it to the airlines," McGee said.