Monday’s incident in which a passenger was dragged from an overbooked United Airlines flight so that employees could fly has prompted new calls for reform.

In a letter from Senators John Thune (R-SD), Bill Nelson (D-Fla.), Roy Blunt (R-Mo.) and Maria Cantwell (D-Wash.) obtained by the International Business Times, the lawmakers called for better ways to deal with similar incidents.

“We recognize the importance of having passengers comply with the lawful instructions of airline crews and law enforcement, but it is hard to believe that some combination of better planning, training, communication, or additional incentives would not have mitigated this particular incident or avoided it altogether,” the senators wrote.

Travel and consumer advocacy organizations like the Business Travel Coalition (BTC) and National Consumer League (NCL) have criticized the airline's handling of the incident.

In a statement on the incident the NCL put the blame on airline consolidation in the United States, which has led to four airlines now flying 80 percent of domestic passengers.

“This latest incident is shocking by any standard and represents a new low for customer service in the airline industry,” said NCL Executive Director Sally Greenberg in a written release. “United had so many other options for handling this unfortunate situation. We all know that when airlines overbook, they offer passengers incentives to volunteer to give up their seats; United should never have escalated the situation and should have offered sufficient incentives to avoid this terrible outcome. The fact that United can get away with this underscores just how few rights consumers have the minute they step into an airport. If the Department of Transportation won’t hold the airlines to account for these practices, then Congress needs to step in and fix the problem.”

The BTC has also called for more competition in U.S. air travel.

“Since the U.S. major network airlines secured their antitrust immunized global alliances, and engineered massive airline industry consolidation, their arrogance has known no bounds,” the BTC said. “They constantly seek to undermine their regulator, the U.S. Department of Transportation, just as they call on the U.S. State Department for protection from competition from best-in-class airlines in their scorched-earth war on U.S. Open Skies policy.”

At the same time, other analysts have pointed out that serious obstacles to change still exist. In an analysis in the Washington Post, PR experts pointed out that consumer outrage from incidents like this tends to be short-lived.

“This will be just a short kind of hit,” Lakshman Krishnamurthi, a marketing professor at Northwestern University’s Kellogg School of Management, told the Post. “Volkswagen had the diesel problem, and their sales are fine. Toyota had a problem years ago, and nothing really happened to their sales.”

Additionally, airline consolidation – which has allowed United to serve more than 50 percent of passenger traffic from major hubs like Houston and Newark – makes it difficult for consumers to carry out boycotts like those that have been suggested on social media.

United’s stock price has already recovered somewhat since CEO Oscar Munoz issued a second apology late yesterday. Shares finished Tuesday down 1.1 percent, an improvement from the 4.4 percent fall earlier that day.

“The truly horrific event that occurred on this flight has elicited many responses from all of us: outrage, anger, disappointment,” Munoz said late yesterday in a new statement on the airline’s website. “I share all of those sentiments, and one above all: my deepest apologies for what happened. Like you, I continue to be disturbed by what happened on this flight and I deeply apologize to the customer forcibly removed and to all the customers aboard. No one should ever be mistreated this way.”

Munoz said that the airline will conduct a review of crew movement, its policies for incentivizing volunteers in these situations, how the airline handles oversold flights and how it partners with airport authorities and local law enforcement. The airline promised to communicate the results of its review by April 30.

fellow passenger posted a Facebook video of the incident, in which United Airlines informed passengers after they had boarded that the plane was overbooked, and four passengers would need to leave in order to allow United Airlines personnel to take the flight to its destination. The airline initially offered an incentive of $400 and a free hotel night, followed by $800. When no passengers volunteered, the airline randomly began selecting passengers to remove. One passenger refused to leave, claiming that he was a doctor who needed to see patients the next day. The airline called security officers, who dragged the man down the aisle and from the plane. That video has since been taken down from Facebook.

The incident followed another recent PR backlash for the airline after it denied boarding to two young girls traveling on discounted non-revenue tickets, because they were wearing leggings that did not conform to the employee dress code.