Conrad Hilton checked into rehab ''almost immediately'' after he was allegedly out of control on an international flight last summer.

The 20-year-old socialite - the younger brother of Paris and Nicky Hilton - appeared in court yesterday (03.02.15) after surrendering to authorities investigating an incident on a flight from London to Los Angeles last July, and it has now emerged that he sought help via a 30-day inpatient drug and alcohol treatment programme after the row, TMZ reports.

Conrad was allegedly handcuffed to his seat after he ''went berserk'' on the flight and threatened crew members, but his lawyer, Robert Shapiro, claimed his actions were the result of an adverse reaction to a sleeping pill.

He was said to have screamed obscenities and threatened flight attendants by shouting: ''I am going to f***ing kill you,'' ''I will f***ing rip through you,'' and ''I will f***ing own anyone on this flight, they are f***ing peasants.''

He is also said to have grabbed a crew member's shirt and shouted: ''I could get you all fired in five minutes. I know your boss! My father will pay this out. He has done it before. Dad paid $300k last time.''

Witnesses claim Conrad then punched the bulkhead of the plane close to an attendant's face and they believe he smoked Marijuana in the bathroom as they could smell the drug.

The captain authorised crew members to restrain him to his seat with handcuffs for the descent.

Conrad admitted he took a sleeping pill before the flight, according to documents, and then bragged about how he ''buried'' the flight attendants, saying: ''I told all of them I could get all of their jobs taken away in less than 30 seconds.''

But his lawyer believes the sleeping pill is responsible for the incident and says there are numerous reports of people experiencing adverse effects, including aggressive outbursts.

Following yesterday's hearing, Conrad was released on $100,000 bail, ordered to surrender his passport and remain in California.