An 80-year-old passenger was exempt from punishment, partly due to her age, after she tossed a handful of coins toward the engine of an aircraft on Tuesday.

The woman, surnamed Qiu, threw nine coins to pray for a safe journey when she was boarding the China Southern Airlines plane at Shanghai Pudong International Airport.

Maintenance personnel launched an immediate overhaul of the aircraft and found one coin in the engine, which could have led to its malfunction. The aircraft departed late on Tuesday evening from Shanghai to Guangzhou, five hours behind schedule.

Authorities said on Wednesday that the woman, who had no criminal record or mental disorder, would be given five days' detention, but the punishment won't apply because she is older than 70 and didn't intentionally sabotage the flight.

Zhang Qihuai, executive vice-president of the Beijing Law Society's Aviation Law Association, said on Wednesday that such actions could lead to up to 15 days in detention and a 500-yuan ($74) fine.

"If that happened on an international airline, she would probably be held criminally responsible, though her age would still be taken into consideration," added Zhang, who is also a research fellow at China University of Political Science and Law's Aviation and Space Law Research Center.

The elderly woman was traveling with her husband, daughter and son-in-law, and was transported to the mobile stairs in a wheelchair due to her decreased mobility.

But as she got to the middle section of the stairs, she tossed nine coins toward the Airbus 320 aircraft.

Passengers behind her reported the incident to crew members.

The 150 passengers were then asked to leave the plane while maintenance staff gave it a thorough examination.

Police said that aside of the coin found inside the engine, the other eight were found on the ground nearby.

It's a common practice for Chinese tourists to throw coins into fountains or onto statues at scenic spots for good fortune.

Following the incident, Southern Airlines alerted passengers to abide by the civil aviation law and regulations, and refrain from harmful activities.

He Qi in Shanghai contributed to this story.