The flight was taxiing towards the runway at San Francisco ahead of take-off for Austin, Texas, when another passenger alerted cabin crew that the man sitting next to her was writing the terrifying note. The captain was warned of the impending threat, and the plane – with more than 100 people on board – hastily turned back to the gate citing mechanical problems.

The man was immediately arrested by airport police who boarded the plane. He was found to be unarmed and is now being evaluated by doctors.

Passenger Vicki Riffe told the New York Daily News she had been sitting in the middle seat when she noticed the man in the window seat scribbling his note: “He started writing extremely fast – with anger. I was scared to death.”

She said the man was grunting as he wrote his threatening message into a notepad. “When I saw that I got scared. I thinking about my kids,” she said.

Police used sniffer dogs to search the aircraft for explosives before it was given the all-clear. However, a dozen passengers decided against continuing their journey.