Air travel in the United States has become a combustible mix in which passengers aren’t the only ones treated unfairly, senators were told Thursday. Travelers all too frequently take out their frustrations on airline employees, including flight attendants and gate agents, speakers said at a Senate hearing.

Senators from both parties said airlines must improve the way they treat passengers, but they also said airline employees must be treated with respect. Lawmakers also revived talk of “Passenger Bill of Rights.”

The Senate hearing comes after a passenger was dragged off a United Airlines flight in April and a n incident on American Airlines in which a mother with a stroller was bullied by a flight attendant.

Videos of both incidents were widely circulated on social media.

“United has clearly begun to take some steps to address this horrific problem,” Minnesota Sen. Amy Klobuchar, a member of the aviation subcommittee, said . But, she added, “I think there may still be a need to put something into law.”

United has said it will reduce the number of overbookings on flights, will no longer call security to remove passengers from planes unless there is a security risk, will implement additional employee training for de-escalating situations and will offer up to $10,000 for volunteers to give up their seat when needed.

Sen. Bill Nelson, D-Fla., said air travelers frequently tell him they “feel like they’re being treated as self-loading cargo rather than as valued consumers.”

Passengers are so fed up that they are becoming amateur detectives, Nelson said, using their cellphones to record incidents such as the removal of United passenger David Dao and the heated confrontation on the American flight.

Widely shared video of a bloodied Dao being dragged from the United flight, which he had refused to leave, sparked worldwide outrage and led to calls for a congressional action.

“I take no pleasure in beating up the airlines, but in this case, it’s warranted,” said Nelson, the top Democrat on the Transportation Committee.

Even as lawmakers spoke, another video surfaced showing a California family who say they were forced off a Delta plane and threatened with jail if they didn’t give up one of their children’s seats .

Sen. Roy Blunt, R-Mo., chairman of an aviation subcommittee, said there are “hard questions” regarding the way frustrated passengers treat airline employees .

Sara Nelson, international president of the Association of Flight Attendants, said United employees have come under siege since the Dao incident.

Complaints and threats have been “pervasive at the airports, on the planes, ” she said.