United Airlines, which is reviewing its policies after the violent removal of a passenger from a flight last week, says it will no longer allow employees to take the place of civilian passengers who have already boarded overbooked flights.

“We issued an updated policy to make sure crews traveling on our aircraft are booked at least 60 minutes prior to departure,” a spokeswoman, Maggie Schmerin, wrote in an email on Sunday. “This is one of our initial steps in a review of our policies.”

Ms. Schmerin confirmed the validity of a memo dated April 14, which was published by TMZ, that ordered the new policy. She said the change was meant to ensure that episodes like what happened last week “never happen again.”