Question: United Express Flight 3411 incident occurred on April 9, 2017, O'Hare International Airport police violently and forcibly ejected passenger David Dao from United Express Flight 3411 after he refused to depart the airplane upon the demand of management, which airline subsidiary operated the scheduled passenger flight, on behalf of United Express?
Sentence (from "United Express Flight 3411 incident"): Prior to the confrontation, managers offered travel vouchers to passengers to vacate their seats to make room for four airline employees who needed to travel to the destination, Louisville International Airport, but none of the fliers accepted.
Relevant evidence: No