Amber Heard accuses 'jealous' Johnny Depp 'kicked her in the back' suspecting affair with co-star James Franco

Los Angeles: Actress Amber Heard says a perceived affair with fellow actor James Franco led to ex-husband Johnny Depp assaulting her on a cross-country flight in 2014.

Taking the stand for a second day as part of a multi-million dollar defamation trial, Heard cast Depp as deeply troubled by jealousy and drugs, reports bbc.com.

Depp is suing Heard for $50 million over an article in which she said she was a victim of abuse, reports bbc.com.

She is countersuing for $100 million.

On Thursday, Heard reportedly said that much of her ex-husband's anger was caused by his belief that she was seeing James Franco, whom she said Depp "hated". Franco starred alongside Heard in 'Pineapple Express' and 'The Adderall Diaries'.

That jealousy, she claimed, led an angry Depp to repeatedly question her on a flight from Boston to Los Angeles, in which he allegedly kicked her.

"He just kicked me in the back. I fell on the floor," she said.

"No one said anything. No one did anything. It's like you could hear a pin drop on that plane."

The court also heard a recording allegedly of Depp on the flight, which Heard said showed him "howling" while suffering from the effects of drug use.

Following the incident, Heard said he met her in New York to apologise and to prove he was sober and committed to change.

Jurors have repeatedly heard about the incident on the flight. In his own testimony, Depp said that he took Oxycodone pills and fell asleep to avoid her.

During her testimony, Depp could sometimes be seen closing his eyes or donning his sunglasses. At one point, he shook his head quietly.

Heard alleged she had the fight with Depp after an argument about his daughter Lily-Rose, who was about 14 at the time.

"She was so young," Heard said. "I felt protective."