Transatlantic flights are bad enough, imagine the horror of having to spend 10 hours cooped up in an enclosed space with a spoiled brat on a drug-fueled meltdown. That's what British-born life coach Patricia Mitchell went through when she flew from London to LA last summer on board the same flight as hotel heir Conrad Hughes Hilton III, younger brother of the famous Paris. Hilton was arrested for his disturbing behavior on board the British Airways flight on July 31, in which he smoked marijuana in a lavatory, threw punches and threatened to 'f****** kill' multiple crew members. On Tuesday, as Hilton celebrated his 21st birthday, GQ published Mitchell's account of the transatlantic flight from hell which ended in Hilton being escorted off the plane in cuffs (though his lawyers have since saved him from any serious punishment). Embarrassing: Hotel heir Conrad Hughes Hilton III turned 21 on Tuesday, but he'll be spending his birthday week in court - pleading guilty to assault for the disturbance he caused on board a British Airways flight this past summer . Famous siblings: BA passenger Patricia Mitchell gave a blow-by-blow account of Conrad's tantrum in a recent story. Conrad pictured above with his very-famous older sister Paris in 2009 . According to an affidavit written by an FBI agent who investigated the incident, Hilton first started to cause a disturbance when he refused to turn off his phone before take off. In a suit: Hilton spotted leaving a federal courthouse in Los Angeles on February 3, 2015 after turning himself in for a public meltdown on the flight. His arraignment is scheduled for Thursday . Just a few minutes later, when the fasten seatbelt sign was still illuminated, Hilton got up from his seat on the second deck business class and went downstairs to wander the plane. Mitchell was seated on the lower deck where Hilton appeared and noted: 'It was during that bit when the stewards are up but nobody else should be. My ears were popping, and I was waiting for the drinks trolley, when suddenly, he's coming down the aisle. I thought, "Whoa, that's not normal." 'He was dressed posh casual, expensive haircut. He looked like a polo player and walked with a sure-footed march, being loud... I heard a lot of "f****." After crew asked him to return to his seat and he refused, Hilton 'threatens to hit someone seated four rows behind him.' Mitchell added, 'I thought he was in the middle of a psychotic episode.' For the next few hours Hilton paces around, swearing and threatening the crew and Mitchell wonders if the plane will be turned around. At one point, Hilton approached a member of the crew to complain about a passenger who was giving him the 'stink eye' when Mitchell considered taking out her phone to record the meltdown. But just one look from Hilton froze her in place. 'He looked at me, really threatening. I don't often watch horror movies, but you know how the walking dead have a look in their eye? I thought, "He's going to come at me next." He turned around and said, "Now everybody's judging me."' The flight attendants then closed the curtains. 'As Hilton wanders around the plane, he lashes out at the customer service manager who is shadowing him to protect the passengers and his 21-member crew,' she added. '"Stop following me!" Hilton yelled, adding: "I am going to f*** kill you!"' Mitchell remembered. He is also said to have screamed, 'I will f****ing own you!' After going back to business class, Mitchell said he 'punched the bulkhead 10 centimeters away from the attendant's head.' Numerous times, Hilton yelled, 'I will f***ing own anyone on this flight; they are f***ing peasants!' according to the complaint. Hilton then reportedly tells other random passengers that  he is already banned by other airlines, has just broken up with a girlfriend, and that his behavior will 'probably turn into a lawsuit for his father to pay.' He then says he wants to smoke marijuana. At 9:15 p.m. 'he locks himself in a lower deck restroom.' 'A smell of weed is detected in the cabin,' according to a report. He then leaves the cabin and goes to the upper deck where he allegedly smokes a cigarette. 'Upon exiting, he surrenders his lighter and cigarettes, returns to his seat and falls asleep,' Wallace reported. An hour later Hilton wakes up and 'approaches yet another flight attendant and says he's "going to f***ing kill" him three times,' it was added. British-born life coach Patricia Mitchell (pictured) reveals details of the flight from hell and describes the temper tantrum thrown by Patrick Hilton after he strolled out of business class and started berating passengers on the lower flight deck, calling them 'f****** peasants' All together: Conrad is pictured with the rest of the Hilton clan at a Christmas Eve dinner. From left: Siblings Paris, Conrad, Barron and Nicky Hilton and their parents Richard and Kathy Hilton . What a parent will do: According to an affidavit of the incident, Conrad claimed at one point to have been banned from other airlines and that the last time this happened his dad paid $300,000. Conrad pictured above with his father Richard in a photo posted to Instagram three weeks ago . 'He grabs the man's shirt and name badge saying, "I could get you all fired in five minutes. I know your boss!" He says, "My father will pay this out, he has done it before. Dad paid $300,000 last time,"' it was detailed in the complaint. He then offered to fight the co-pilot. After several more outbursts, the co-pilot 'comes out from the flight deck to present Hilton with a final written warning. Hilton rips it up.' At 2:20 a.m. London time, 'a second safety briefing is held to discuss restraining Hilton, who is again asleep,' reported Wallace. Hilton is then handcuffed while asleep. When he awakes he starts screaming. 'A buzz went around the plane that he had been restrained and we were all, "Fantastic. Good. Happy about that,"' added Mitchell. At about 3:15 a.m. London time [8:15 p.m. Los Angeles time], Flight 269 lands. Police come aboard and escort the handcuffed Hilton to the terminal, it was detailed in the affidavit. 'I remember coming off and seeing him sitting on a bench with what I assume was some kind of federal agent. You would have thought butter wouldn't melt in his mouth, he was so cool. He looked all innocent, like, "I don't know what the fuss is all about,"' said Mitchell. Her two brothers: Paris - now 34-years-old - pictured with both Conrad and Barron on the beach in 2014 . His other famous sister: Conrad with Nicky, 31, a fashion writer and fiancee of James Rothschild . Hilton's lawyer, Robert Shapiro, told TMZ.com that Hilton took a sleeping pill before the flight, which may have caused his behavior. Shapiro also said Hilton voluntarily checked himself into a 30-day rehab program after the flight. On February 2, Hilton was charged with intimidating or assaulting the flight crew to the point where he interfered with their ability to perform their duties - a crime which carries a sentence of up to 20 years in prison. He was released on $100,000 bail and just last week his lawyers struck a plea deal, in which he will plead guilty to one count of simple assault which has a maximum sentence of six months in jail, a year of probation and fine of $5,000. He will hear his sentence on Thursday. No one had heard of Hilton's in-flight meltdown until February when a federal criminal complaint was filed. Hilton was travelling aboard an AIRBUS A380 and was sat  on the top deck before he wandered down stairs and started abusing other passengers .
Conrad Hughes Hilton III was arrested after causing a disturbance on board a British Airways flight from London to LA last July . Passenger Patricia Mitchell says the hotel heir smoked marijuana in a bathroom and was threatening to the crew . Last week, the 21-year-old struck a plea deal with prosecutors to downgrade the charges to simple assault . He is due back in court for sentencing on Thursday .