A Capital Airlines flight bound for Nha Trang, Vietnam, took off from Hangzhou, Zhejiang province, on Tuesday but was forced to return because of an unspecified mechanical problem, the airline company said in a statement.

Capital Airlines Flight JD421, was scheduled to take off from Hangzhou Xiaoshan International Airport at 1:55 pm on Tuesday and was due at Vietnam's Cam Ranh International Airport in Nha Trang at 4:50 pm.

The flight was delayed nearly two hours and departed at 3:15 pm, China Central Television reported. About an hour later, the airline determined that the plane needed to return because of mechanical issues.

Passengers on the airplane said the return was triggered by a crack in a window pane, but that was not verified by the airline company or the airport, according to Urban Express, a media outlet in Hangzhou.

The flight was bumpy and descended rapidly after the change was announced, passengers said.

"It was just like sitting on a Giant Drop"-an amusement-park ride-a passenger surnamed Fang told Beijing News.

She said the bumpy ride lasted for five to six minutes, which made her so nervous that her legs were shaking as she got off the plane.

A total of 211 passengers were on the aircraft. Capital Airlines paid each passenger 400 yuan ($62) in compensation, as required by regulations, CCTV reported.

A new aircraft was arranged to replace the original one, and it took off at 11:35 pm on Tuesday.

Capital Airlines, based in Beijing, is a subsidiary of HNA Group. The problem aircraft was an Airbus A321.

Two weeks ago, a flight operated by Sichuan Airlines was forced to divert to Chengdu en route from Chongqing municipality to Lhasa, in the Tibet autonomous region, after a windshield blew out in the cockpit.