The attendant said the first incident lasted three or four seconds. “He used his hand to touch the left side of my buttocks and told me somebody was walking behind me.”

The second incident lasted a few seconds, she said.

X’s colleague Soko Kobayashi, a flight purser who witnessed the second alleged attack, said she saw Amstutz touch X’s buttocks with his hand.

“[X] was standing next to 43C and was about to cry,” she said.

Kobayashi said she was not sure how long the entire incident lasted, but she witnessed it for about two seconds.

The alleged assault took place before take-off, and Amstutz was removed from the plane after the case was reported to the captain. He was then arrested by police.

Amstutz, who was a woodworker before retiring, said in the witness box that he only touched the small of X’s back to prevent her from bumping into other colleagues who were walking down the aisle.

“I put the hand on the small of her back … to protect Madam X from a collision with her colleagues,” he said, adding that the touch was “in no way indecent”.

Under cross-examination by prosecutor Henry Cheng, Amstutz admitted he did not give X any verbal warning as to the potential risk of a collision.

“It happened so quickly. What should I say?” he said.

Although there was no danger of anyone tripping, he said: “Half of the aisle was occupied by X. If she moved back, [X and her colleague] would have run into each other.”

Defence lawyer Phil Chau said there was neither groping nor finger movements after Amstutz rested his hand on the back of X.

He said X had accepted there were flight attendants walking past her when Amstutz put his hand on her back. “[It] gave the defendant a legitimate reason … to prevent her from colliding with other people.”

The court heard that Amstutz, who had intended to fly to Switzerland to visit his seriously ill mother, had stayed in Hong Kong for one month due to the court proceedings.

Magistrate Rita So Ka-yin will give her verdict tomorrow.