United is taking steps too. It will require employees seeking a seat on a plane to book it at least an hour before departure, a policy that might have prevented last Sunday's confrontation.
Those and other changes show airlines are scrambling to respond to a public-relations nightmare - the video showing airport officers violently yanking and dragging 69-year-old David Dao from his seat on a sold-out United Express flight.
Dao and three others were ordered off the plane after four airline employees showed up at the last minute and demanded seats so they could be in place to operate a flight the next day in Louisville, Kentucky.
On Friday, a United spokeswoman said the airline changed its policy to require traveling employees to book a flight at least 60 minutes before departure. Had the rule been in place last Sunday, United Express Flight 3411 still would have been overbooked by four seats, but United employees could have dealt with the situation in the gate area instead of on the plane.
Delta Air Lines is moving to make it easier to find customers willing to give up their seats. In an internal memo obtained Friday by The Associated Press, Delta said gate agents can offer up to $2,000, up from a previous maximum of $800, and supervisors can offer up to $9,950, up from $1,350.
United said it is reviewing its compensation policies. The airline would not disclose its current payment limit.
Other airlines said they were examining their policies. American Airlines updated its rules to say that no passenger who has boarded the plane will be removed to give the seat to someone else.
None would describe their limits on paying passengers.
When there aren't enough seats, airlines usually ask for volunteers by offering travel vouchers, gift cards or cash.
Last year Delta got more passengers to give up their seats than any other U.S. airline, partly by paying more than most of the others.
As a result, it had the lowest rate among the largest U.S. airlines of bumping people off flights against their will - something that is legal but alienates customers and requires the airline to pay compensation of up to $1,350 per person.
Overselling flights is a fact of life in the airline business. Industry officials say that it is necessary because some passengers don't show up, and that overbooking keeps fares down by reducing the number of empty seats.
The practice has been questioned, however, since video of the United Express incident went viral. United Continental CEO Oscar Munoz's initial attempts to apologize were roundly criticized. On Friday, company Chairman Robert Milton said the board supported Munoz.
"We need to use this regrettable event as a defining moment and pivot off it to craft friendly policies," Milton said in a note to employees.
The dragging has turned into a public-relations nightmare for the entire industry, not just United, and led to calls from politicians and consumer advocates to suspend or ban overbooking.
Ben Schlappig, a travel blogger who first wrote about the Delta compensation increase, said it shows Delta is trying to reduce forced bumping. He said he couldn't imagine many situations in which people wouldn't jump at nearly $10,000.
Delta no doubt hopes that gate agents and their supervisors won't need to make maximum offers, and the financial cost to the airline is likely to be limited. If Delta paid $9,950 to every person it bumped involuntarily last year, that would total $12 million. Delta earned nearly $4.4 billion.
Raising the limits "lets them solve some PR problems" and might head off U.S. Transportation Department regulations to curb overbooking, said another travel blogger, Gary Leff. "They can say, 'Look, we're already solving the problem.'"
An AP analysis of government data shows that in 2015 and 2016, Delta paid an average of $1,118 in compensation for every passenger that it denied a seat. Southwest Airlines paid $758, United $565, and American Airlines $554.
After the incident in Chicago, critics questioned why United didn't offer more when no passengers accepted the airline's $800 offer for volunteers to give up their seats.
"If you offer enough money, even the guy going to a funeral will sell his seat," said Ross Aimer, a retired United pilot.