United Airlines faced calls for a worldwide boycott yesterday despite the head of the airline issuing a second statement apologising over the enforced removal of a passenger.

Shares in the carrier’s parent company recovered some ground after stock fell 4% at one point before losses narrowed to finish down 1%.

Videos of the passenger being dragged off a United flight in the US sparked outrage on social media.

Tens of thousands of potential passengers took to Facebook and Twitter last night to demand a boycott of the airline, which flies to 339 destinations in 54 countries, The Times reported.

A petition calling for Munoz’s resignation attracted almost 20,000 signatures.

Anger against the carrier, whose slogan is “fly the friendly skies”, mounted after its CEO appeared to defend its actions, blaming the passenger for being “disruptive and belligerent”.

Oscar Munoz told staff in an email that the passenger was initially “politely asked to deplane” and the row erupted only when he refused.

He backed employees for going “above and beyond to ensure we fly right”, adding: “This is an upsetting event to all of us here at United.”

However, he later issued another statement, giving his “deepest apologies” for the “truly horrific event”, saying: “I continue to be disturbed by what happened on this flight and I deeply apologise to the customer forcibly removed and to all customers on board. 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.”

Munoz announced a “thorough review” of crew movement, policies for incentivising passengers in such situations, how the airline handles oversold flights and an examination of partnerships with airport authorities and local law enforcement.

He pledged to publish the results of the probe by the end of the month.

The passenger was later named as David Dao, a 69-year-old Vietnamese-American doctor and father of five.

The grandfather was dragged off the aircraft at Chicago O’Hare international airport in on Sunday. It was bound for Louisville, Kentucky.

The airline said that up to $1,000 in compensation, along with a hotel room and a flight the next day, had been offered to create space for four staff members who needed to be in Louisville.

Dr Dao refused to leave after being randomly picked to “voluntarily” give up his seat, insisting that he needed to see patients the next day.

Film shot by other passengers and shared on social media showed him screaming as he was manhandled by three security staff, before hitting his head on an armrest and being dragged away with a bloodied face.

Critics also flooded social media with jokes about United.

One said: “United is proud to announce the new club class! Fight Club”.

Another pictured an armed Swat team, with the label that it was the airline’s new special seating division.

One asked what the cheaper way to get sore teeth removed in the US was, the dentist or a flight with United.

In China the video has reportedly been watched more than 100 million times and was the most popular topic on Weibo, where the boycott campaign gained huge support. Many complained that the passenger was picked on because he looked Chinese.

One social media user wrote: “Simple fix. Do not overbook your seats and stop beating up your passengers. Boycott United.”

The Chicago incident came just weeks after the carrier was criticised on social media for refusing to allow two teenage girls to board a flight because they were wearing leggings.