Following his initial defiance over the incident, Oscar Munoz has now said sorry for the way the passenger was handled during what he called a "truly horrific event".

Footage of a bloodied United Airlines passenger being dragged off an overbooked flight in Chicago on Sunday night has since gone viral.

In a statement to his team released on Tuesday, Mr Munoz said: "The truly horrific event that occurred on this flight has elicited many responses from all of us: outrage, anger, disappointment.

"I share all of those sentiments, and one above all: my deepest apologies for what happened.

"Like you, I continue to be disturbed by what happened on this flight and I deeply apologize to the customer forcibly removed and to all the customers aboard. No one should ever be mistreated this way.

"I want you to know that we take full responsibility and we will work to make it right."

The letter shows a stark change in tone from an initial memo to employees in which Mr Munoz was unapologetic, blaming the incident on the fact that the passenger had "defied" security officers.

The first memo said there were lessons the company could learn, though he stressed that he "emphatically" stood behind his employees.

However, the second letter sent out to the team shows an about-turn, with the airline's chief executive showing absolute contrition.

The statement continues: "It's never too late to do the right thing. I have committed to our customers and our employees that we are going to fix what's broken so this never happens again.

"This will include a thorough review of crew movement, our policies for incentivizing volunteers in these situations, how we handle oversold situations and an examination of how we partner with airport authorities and local law enforcement.

"We'll communicate the results of our review by April 30th. I promise you we will do better."

Munoz acted after shares in the airline's parent company United Continental Holdings fell 4% earlier on Tuesday.

Investors appear to have become increasingly anxious as people kept watching and sharing the footage - including 130 million views on China's Weibo social media platform by Tuesday afternoon.

After his latest statement they recovered much of the losses to settle 1.5% lower.

The company earned about 14% of its annual revenue last year by flying Pacific routes.

Following the incident on Flight 3411, the Chicago Department of Aviation has confirmed that one of its officers had not followed protocol and has been placed on leave pending a review of his actions.

Additional reporting from IRN