Spring Break is turning out to be a breaking point for two airlines, United and Delta.

There is rightly outrage at the sight of law enforcement officers forcefully removing a United passenger because he refused to give up his seat on an overbooked flight.

Passengers boarding United Flight 3411 from Chicago to Louisville were told it was overbooked. The airline offered $400 and a hotel stay to people who would switch flights voluntarily, but there were no takers.

Then, when all the seats were occupied, the airline announced that four seats were needed for a United crew who had to be in Louisville the next morning. The offer for volunteers was doubled to $800 and one couple agreed to switch.

Nobody else followed. A manager announced that a computer would choose who had to go. Police then came on board and instructed a passenger he had to give up his seat. He refused, and video of the incident shows him being manhandled from the airplane.

According to an eyewitness the man said he was a doctor who had to see a patient at a hospital in the morning.

“Everyone was shocked and appalled,” said the eye witness.

United’s CEO, Oscar Munoz, hardly improved the impression of the airline’s attitude in a statement that resorted to the euphemism, “having to re-accommodate these customers” when describing what happened and said his airline was “reaching out” to the specific victim to “further address and resolve this situation.”

United has become notorious for heavy-handed treatment of passengers. Two weeks ago two teenage girls were stopped from boarding a flight from Denver to Minneapolis because they were wearing leggings. They were allowed to board only after putting on dresses.

This problem goes back to the creation of an airline monster that nobody seems able to manage – the merger of United and Continental in 2010. This was one of the steps leading to the creation of what has become an oligopoly of the three largest domestic carriers. In the case of United, it turned out to be a deeply troubled transition, with mismatched company cultures, overlapping routes that were difficult to reconcile and deteriorating staff morale that met passengers at every gate.

As a result United’s financial performance has lagged behind competitors, Delta and American, particularly in its domestic operations. And that, in turn, has put managers under pressure to put profit before passengers.

The airline’s head of finance, Gerry Laderman, told an industry conference in Dublin last month, “We need to get back in the game domestically.”

They are well short of that. The overbooking episode in Chicago is worse even than it might appear, showing how far United has to go.

Overall last year American carriers were doing well in efficiently managing their capacity to avoid the curse of overbooking. The way airlines measure bumped passengers is reduced, ridiculously, to decimal points and so the statistic looks strangely detached from actual people, but only 0.62 of every 10,000 passengers were bumped from flights they had booked in 2016, the lowest rate since 1995.

Overbooking is legal but it leaves such damage to customer relations, not to mention passengers’ travel plans, that no airline wants it to happen. It always results from a calculated gamble – that a small number of booked passengers will be no-shows. Mostly, that works out but in this case United seems to have exacerbated the problem by insisting that its flight crew in transit got priority over passengers.

United is huge. It has hubs at Chicago, Newark, Los Angeles, Washington, Houston, Denver and San Francisco. Spring Break was always going to produce peak traffic and, clearly, the Chicago debacle has exposed that the airline is still not up to the simple challenge of respecting its passengers and, at the same time, rebuilding its business.

Delta, an airline with a better reputation, has also been caught out by Spring Break pressures. One day of thunderstorms in Atlanta last week paralyzed Delta’s whole domestic network. They canceled 3,300 flights over five days, much worse than even last year when the failure of a single piece of electrical equipment in Atlanta shut down the whole worldwide computer system. That led to 2,300 cancellations.

This time there were widely seen images of people sleeping in the terminal at Atlanta, stories of people boarding flights that were then put on ground stop until the crew’s legal work hours expired, returning to the gate, getting on another flight only to repeat the experience. The final twist of the knife was that passengers who tried to escape by taking a rental car found that there were no rentals left.

A Delta spokesman, Gil West, said, “We as always learn from these experiences…while we can’t control the weather we understand that the resulting recovery has not been ideal and we apologize for that.”

As for Scott Kirby, the new president of United, who left American Airlines last year to take on the job, he seems to be in the process of discovering that he inherited the worst nightmare of an airline in an industry that has a long way to go before passengers will get the standards of service that they have every right to expect.