Shares in United Continental, the parent company of United Airlines, have dropped by almost four per cent in early trading across the Pond.
The stock's decline follows a rocky couple of days for the airline, which hit headlines around the world after footage of a passenger being dragged off one of its flights went viral online.
The passenger, who has been identified as Dr David Dao, was removed from flight 3411 from Chicago to Louisville because it was overbooked. The airline said passengers were asked to volunteer to get off the plane, and when they didn't, a few people were told they must take another flight.
“This is an upsetting event to all of us here at United," said United chief executive Oscar Munoz in response to the incident.
"I apologise for having to re-accommodate these customers. Our team is moving with a sense of urgency to work with the authorities and conduct our own detailed review of what happened. We are also reaching out to this passenger to talk directly to him and further address and resolve this situation."
However, in a letter to staff Munoz appeared to blame Dao for being "disruptive and belligerent", and said he "emphatically stands behind" his staff.