A passenger on Australian budget carrier Jetstar threw open an emergency door and exited by clambering over the wing and engine after landing in Melbourne on Thursday, officials said.

Australian federal police arrested the man following his unauthorised departure from the Sydney-Melbourne flight.

"We can confirm that a passenger opened the emergency exit door after arrival into Melbourne, which automatically deployed the slide," a Jetstar spokesperson said.

"The plane was parked at the gate."

After leaving by the emergency exit door, the man walked along the wing before making his way down to the ground via the engine, officials said.

Audrey Varghese, a fellow passenger on the flight, told Melbourne radio 3AW that the man had been exhibiting "quite strange behaviour", ignoring the seatbelt signs and multiple requests by flight attendants for him to remain seated.

"People thought that was quite strange. And then as soon as the plane had started to come to a stop, he immediately got up and basically charged to where the emergency exit row is," she said.

In the process, he was "shoving people, causing a bit of commotion," Varghese said.

He then "ripped open" the emergency door, deploying the slide, and "jumped off the plane".

Varghese said there were "screams and shrieks" from other passengers, who were obviously "very frightened".

"I think people were just screaming because of how strange this behaviour was."

Federal police said they arrested a man for "alleged aggressive behaviour and breaching aircraft safety protocols on a domestic service".

"The man was assessed by ambulance officers and later transferred to hospital for further assessment, where he remains," a police spokesperson said.

Police said they were still investigating but charges were likely to be laid "at a future date".

Jetstar, a subsidiary of Qantas, said it wanted to thank passengers for their "patience and understanding" during the incident.