On Sunday and Monday, United Airlines insisted that the incident that led to Dr. David Dao being forcibly removed off a United Express flight from O’Hare Airport to Louisville happened because the plane was overbooked.

But on Tuesday, the airline took that back.

All 70 seats on the United Express flight were full, meaning it wasn’t oversold. Rather, the airline needed to make room for a crew of four that needed to get to Louisville for a flight the next day.

“The flight was not oversold,” United spokeswoman Maddie King said Tuesday. “There was a United Express crew that needed to get to Louisville to prevent a flight down the line from canceling.”

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Airlines often oversell flights, end up bumping passengers

Once the plane had boarded, nobody volunteered to accept a financial incentive to leave it, passengers said, so airline workers selected four people — including Dao — to get off.

The passengers were selected based on a combination of criteria spelled out in United’s contract of carriage, including frequent-flier status, fare type, check-in time and connecting-flight implications, among others, USA Today reported, quoting the airline.

Airlines are allowed to oversell flights, and they frequently do, because they assume that some passengers won’t show up. U.S. airlines bumped 40,000 passengers last year, not counting those who volunteered to give up their seats, the Associated Press reported.

Contributing: Sun-Times wires