The once-friendly skies just keep getting nastier.

​A Manhattan socialite whose pals include first daughter Tiffany Trump ​​is suing United Airlines saying she was traveling to London last year ​when she was yanked out of business class​ by an attendant​, cursed at and ​ultimately ​forced into a middle seat in the back of the plane.

Karen Shiboleth, the Instagram-loving daughter of wealthy New York lawyers, was headed to the UK from Newark Liberty International Airport to start a master’s degree program in international relations at Kings College on Sept. 10, 2016.

She’d originally paid $1,500 for a window seat in economy. Then she used American Express points plus $500 in fees to upgrade to an economy plus seat. Finally, when she was at the airport, she upgraded again, forking over an additional $1,150 for business class seat 1B.

The 24-year-old, whose mother was general counsel to Revlon, says she paid the extra money to be near the front of the plane because she was traveling with “heavy luggage and large carry-on bags which contained a significant amount of her personal belongings and valuables.”

Shiboleth, who has over 15,000 Instagram followers, regularly jets out of town to ritzy locals like Aspen, Co. and Miami Beach, FL. Her social circle includes President Trump’s youngest daughter Tiffany Trump and model Stephanie Seymour’s son Peter Brant Jr.

Last September, she had been in her roomy seat for 20 minutes when — just 10 minutes before takeoff — a United gate agent rushed onto the plane, the Manhattan civil suit says.

Employee Eunice Daly “without explanation demanded that [Shiboleth] vacate her seat in United BusinessFirst and move to the back of the boarded plane to seat 21B,” the Manhattan Supreme Court suit says.

Shiboleth says Daly initially refused to identify herself, covering up her name tag when the passenger tried to look. She was shocked by Daly’s demands, especially given that there were other open seats in the business class cabin, the suit says.

When Shiboleth protested and showed her ticket for the first-row seat, Daly “took [her] arm without consent and forced [her] to a middle seat in the back of the plane,” the suit alleges.

“Daly further insulted and humiliated [Shiboleth] by raising her voice and calling [her] a ‘c–t’ in front of other passengers,” according to court papers.

She “was paraded to the back of the plane in tears,” the suit says.

The flight attendants later apologized for the incident, but Shiboleth was only offered a $750 voucher. She had paid over $3,000 for the business class seat, the suit says.

She’s never used the voucher and is suing for $9,146 in awards points and fees and $150,000 in punitive damages to “deter such behavior in the future.”

A United spokeswoman said, “Our goal is to provide all our customers with a great travel experience. We are aware of the filing and reviewing it, but due to pending litigation we are unable to comment further.”

The airline has been struggling to recover from a public relations disaster after a video surfaced of a passenger being bloodied and dragged out of his seat on a flight from Chicago on April 9.