United is taking steps too. When Dao refused, United called airport police, who dragged him off the plane.
A United spokesperson told TMZ the change was made "to make sure crews traveling on our aircraft are booked at least 60 minutes prior to departure".
In a memo to employees obtained by the Atlanta Journal-Constitution, Delta said the decision was to "reinforce our commitment to our agents and their ability to care for our customers".
Delta Air Lines is moving to make it easier to find customers willing to give up their seats.
ATLANTA -Delta customers can now be offered almost $10,000 for giving up their seats on overbooked flights.
Meanwhile, United is re-working parts of its overbooking policy that were at fault in the incident. The airline would not disclose its current payment limit.
It's no surprise airlines would want to beef up the incentives for customers they need to bump from flights.
None would describe their limits on paying passengers.
Delta had one of the lowest rates of involuntary boarding denials among US carriers past year at one per 100,000 passengers.
As a result, it had the lowest rate among the largest USA 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.
Furthermore, Delta was among the best airlines at not booting passengers involuntarily. 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 question followed controversy regarding airlines' overbooking practices in the wake of the United incident on 9 April. It's more than seven times higher than the previous limit of $1,350 paid to passengers who help the airline out when it sells more tickets than it can accomodate.
Delta involuntarily bumped travelers just once in every 100,000 flights. "They can say, 'Look, we're already solving the problem'".
Here's how much cash Delta paid out in compensation to the average passenger who was denied boarding in 2016: $9. Southwest Airlines paid $758, United $565, and American Airlines $554. Passengers said the offers stopped at $800.