United Airlines has changed its policy on giving staff last-minute seats on full flights following the fallout from it dragging a screaming passenger from a plane.

Dr David Dao lost two front teeth and suffered a broken nose after he was forcibly removed from the overbooked flight from Chicago to Kentucky last week so a member of staff could take his seat.

Footage of the incident, where several security officers dragged Dr Dao’s hands and legs from the plane, was shared widely on social media.

A leaked letter to employees by United’s chief executive Oscar Munoz revealed the crew had been trying to make space for four employees of a partner airline.

He said the staff had first asked for volunteers to get off the plane and offered $1,000 in compensation, but when no one volunteered they approached individual passengers to deny them boarding.

Three agreed to leave but Dr Dao, who said he needed to return to Kentucky to treat patients the next day, refused and told them they would need to drag him off.

Mr Munoz claimed Dr Dao had been “disruptive and belligerent” but made no mention of the use of excessive force in the initial email.

The 69-year-old's lawyer said he will need to have reconstructive surgery and has announced he plans to sue the airline.

The world's 10 worst airlines Show all 10 1 /10 The world's 10 worst airlines The world's 10 worst airlines 10. Jet AirHelp, has assessed more than 30 airlines using scores for quality of service, on-time performance and responses to claims for compensation. Here follows the lowest ranked airlines, starting with Jet Airways, 35% of whose flights were delayed in 2018 Getty The world's 10 worst airlines 9. Aerolineas Argentinas 15% of Aerolineas Argentinas flights were delayed in 2018 Getty The world's 10 worst airlines 8. Iberia 16% of Iberia flights were delayed in 2018 Getty Images The world's 10 worst airlines 7. Korean Air 36% of Korean Air flights were delayed in 2018 Getty The world's 10 worst airlines 6. Ryanair 14% of Ryanair flights were delayed in 2018 EPA The world's 10 worst airlines 5. Air Mauritius 31% of Air Mauritius flights were delayed in 2018 Getty The world's 10 worst airlines 4. easyJet 21% of easyJet flights were delayed in 2018 AFP/Getty Images The world's 10 worst airlines 3. Pakistan International Airlines 39% of Pakistan International Airlines were delayed in 2018 Getty The world's 10 worst airlines 2. Royal Jordanian Airlines 13% of Royal Jordanian Airlines flights were delayed in 2018 Getty The world's 10 worst airlines 1. WOW Air 25% of WOW Air flights were delayed in 2018 Getty

His daughter, Crystal Dao Pepper, later told a news conference in Chicago that the family had been “sickened” by the incident and his lawyer described it as worse than what he had experienced while fleeing Vietnam.

The airline has now said in future that any crew members that needed to travel would be allocated seats at least an hour before departure.

The company said the move was aimed at improving its customer service.

Mr Munez later apologised for the incident after online petitions calling for his resignation reached thousands of signatures.

In a statement he said: “This is an upsetting event to all of us here at United. I apologise for having to reaccomodate these customers.”

He said he felt “shame and embarrassment” and it would never happen again.