United Airlines made a policy change Friday that all crew members traveling on its planes must arrive at least 60 minutes before departure, so as not to displace passengers who have boarded aircraft.

Airlines were scrambling to review and revise policies, after United Airlines passenger David Dao was dragged off a Louisville, Ky.-bound flight in Chicago to make room for United crew members.

Delta Air Lines said Friday that gate agents can now offer up to $2,000, an increase from $800, and that supervisors can offer up to $9,950, up from $1,350 in compensation to passengers who voluntarily give up seats on overbooked flights.

In statement reported by Business Insider, United said, "We issued an updated policy to make sure crews traveling on our aircraft are booked at least 60 minutes prior to departure. This ensures situations like Flight 3411 never happen again. This is one of our initial steps in a review of our policies in order to deliver the best customer experience."

When Dao, 69, was forcibly removed from his flight, videos shot by other passengers went viral, prompting international outrage and calls for Congress to enact reforms — and for airlines to better explain procedures on bumping paying passengers.

United announced it was examining policies governing customer service, employee training, and handling oversold flights. It said it would announce the results and any actions by April 30.

After the uproar over the mistreatment of Dao, who suffered a concussion, a broken nose, and lost two teeth, U.S. carriers are scrutinizing their policies, said Henry Harteveldt, a travel-industry analyst.

Airlines are looking at compensation levels so gate agents can offer more money without a supervisor's approval, Harteveldt said.

"I have learned from various airlines that they have begun to reexamine how many people they will overbook when they overbook a flight, what their policies will be, how they will handle getting people to voluntarily give up their seats in exchange for compensation." he said. "Airlines know that if they fix the problem themselves, it reduces the chance of government regulators telling them what to do. I think this incident will spark some meaningful change."

Dao, 69, was on United Express Flight 3411, operated by regional carrier Republic Airlines, from Chicago O'Hare International Airport to Louisville. The flight was full but not overbooked. Passengers had already boarded when four Republic crew members showed up, saying they needed to get to Louisville to operate another flight.

When United could not get four volunteers to leave the plane, they selected four. Dao refused to get off and was dragged away, his face bloodied.

Kevin Mitchell, chairman of the Business Travel Coalition in Radnor, said the incident "galvanized the problem we have in the U.S. airline industry."

What's needed is "a culture change" that puts passengers first, Mitchell said. Foreign carriers such as Japan Airlines and Singapore Airlines put their customers on a pedestal and treat them as guests, he said. U.S. airlines should stop overbooking flights, and instead charge "no show" passengers a $200 fee in addition to the ticket price. Airlines would get an extra $200 and could then sell a walk-up fare to standby travelers, Mitchell said.

U.S. Sen. Richard Blumenthal (D., Conn.) plans to announce legislation Monday for an airline passenger bill of rights, requiring minimum cash compensation for involuntary bumping, limitations on the use of police to forcibly remove passengers, and restrictions on airlines' ability to bump passengers to accommodate crew or elite-level passengers.

The bill also would allow passengers to sue airlines for unfair and deceptive practices such as tarmac delays, undisclosed fees, price gouging, chronically late flights, or health and safety risks.

The National Consumers League blames airline consolidation — with four big carriers (United, Delta, American, and Southwest) flying 80 percent of U.S. passengers — for more crowded planes, shrinking seats, extra fees, and reduced flight service to smaller cities.

"We are urging members of Congress to use this as an opportunity to put in place consumer protections that currently either don't exist or aren't being enforced by the Department of Transportation," said Sally Greenberg, the group's executive director. "This is a great time to say, 'Enough, already,' to the airlines."

Among the changes the consumers league would like to see: Get rid of flight cancellation fees, often $250 to change a reservation; let passengers choose their seats and have full access to the aircraft seating chart; stop airlines from cramming more, and smaller, seats into the coach cabin, creating a safety hazard, the group said.