So much for flying the friendly skies.

United suffered another major public-relations disaster over the weekend when a passenger was forcibly dragged off a flight so the airline could make room for an employee trying to make a connection — and the feds are now investigating the disturbing incident.

The booted passenger was caught on video kicking and screaming hysterically as he was hauled off Flt. 3411 from Chicago on Sunday, with the footage spreading like wildfire on social media Monday.

According to people on the plane the man, identified by the Louisville Courier-Journal as David Dao, who appeared to suffer an injury to his mouth, claimed to be a physician and said he couldn’t de-board because he had patients to see.

“The doctor needed to work at the hospital the next day,” Twitter user Jayse D. Anspach wrote in a series of tweets, which were accompanied by several videos showing the incident unfold.

“So he refused to ‘volunteer,’ ” Anspach added.

United CEO response to United Express Flight 3411. pic.twitter.com/rF5gNIvVd0 — United (@united) April 10, 2017

United spokeswoman Maddie King told The Post on Monday that the man refused to get off the plane and was eventually forcibly removed to make room for a crew member who needed to catch a “downline connection” in Louisville later that night. The airline employee was one of four workers who had to board the flight to make their connection, she said.

King said United would have been forced to cancel that flight — inconveniencing even more passengers — had it not gotten the employees on board.

“[The crew] asked for four volunteers, didn’t get the number of volunteers we needed, so began approaching individuals one by one,” King explained.

“We had three customers who deplaned when they were requested, and we also had an additional customer who was asked to deplane repeatedly, and he refused.”

The incident unfolded at Chicago O’Hare International Airport — exactly two weeks after United’s yoga-pants debacle, in which several young girls flying as friends and family of United workers were barred for wearing the stretch pants.

Sunday’s incident is now being investigated by the federal Department of Transportation to determine whether the airline complied with regulations on removing passengers.

Another video posted by Audra Bridges on Sunday night shows authorities plucking the screaming man out of his seat and down the aisle.

If you visit the USA, never ever EVER fly with United Airlines. Here is innocent customer in trauma after being assaulted on the plane pic.twitter.com/INPYckM5m9 — The Pileus (@thepileus) April 10, 2017

At one point, the man ran to the back of the plane — where he was caught on video looking dazed and disoriented.

“They kill me,” he can be heard saying, blood smeared across his face.

“They kill me, they kill me.”

Other passengers looked on in horror.

“Oh my God! What are you doing?” one woman is heard saying in the clip.

Bridges told the Courier-Journal of Louisville that passengers had been informed at the gate that United was offering $400 and a hotel stay for a volunteer who would agree to take another flight at 3 p.m. Monday.

After everyone boarded, the airline then told the man and three others that they had to give up their seats.

United would have selected the four passengers based on several factors, including his or her “fare class, itinerary, status of frequent-flier program membership, and the time in which the passenger presents him/herself for check-in without advanced seat assignment,” according to its “Contract of Carriage’’ rules.

Passengers were told the flight would not take off until they made room for the crew, Bridges said — and the compensation was increased to $800 — but still, no one took the offer to give up the final seat.

Officials said a pair of security guards with the Chicago Department of Aviation had tried talking the man into leaving, to no avail. A third later arrived and threw the passenger against the armrest before the guards dragged him out of the plane.