An elderly woman has delayed a plane for more than five hours, after she attempted to throw a handful of coins into its engine for good luck.

The passenger was boarding China Southern Airlines flight CZ380, from Shanghai to Guangzhou, when she threw nine coins towards the plane's jet engine.

The coin toss was quickly noticed by a fellow passenger, who was able to alert authorities before take-off.

The coins, worth about 1.7 yuan ($0.35) altogether, caused 150 passengers to evacuate as the airline conducted a full inspection of the plane's engine.

Police were called to Shanghai Pudong International Airport and the elderly passenger, who had been travelling with her husband, daughter and son-in-law, was taken away for questioning.

They later confirmed the passenger, surnamed Qiu, had thrown the coins "to pray for safety" and they had been informed by a neighbour that she "believes in Buddhism".

The plane was finally able to take off safely at 5:52pm local time (7:52pm AEST), more than five hours late.

China Southern Airlines reminded all passengers to comply with civil aviation laws in a post on social media site Weibo, and to avoid any behaviour that could jeopardise the safety of their fellow passengers.