Photos: IC

Boeing announced Thursday up to 50 of its popular 737NG planes had been grounded ­after cracks in them were detected, in another blow to the US aircraft maker following two ­deadly crashes.

Australian national carrier Qantas became the latest airline to take one of the planes out of the air, as it said it would urgently inspect 32 others but insisted passengers had nothing to fear.

The announcement by Qantas came after authorities in Seoul said nine of the planes were grounded in South Korea in early October, including five operated by Korean Air.

Boeing had previously reported a problem with the ­model's "pickle fork" - a part which helps bind the wing to the fuselage.

This prompted US regulators to early last month order immediate inspections of aircraft that had seen heavy use.

Following the Qantas announcement, a Boeing spokesperson on Thursday told AFP in Sydney that less than 5 percent of 1,000 planes had cracks detected and were grounded for repair.

The spokesperson did not give an exact figure, though 5 percent equates to 50 planes of 1,000 inspected.

Boeing and Qantas stressed travelers should not be concerned. 

The NG is a precursor plane to the Boeing 737 MAX, which has been grounded since mid-March following the two deadly crashes in Indonesia and Ethiopia. 

Boeing is still trying to restore its safety reputation ­after two 737 MAX crashes last year that killed 346 people and highlighted problems with the planes' flight handling software.