Photo:VCG

Australian airline Qantas has pulled three of its Boeing 737 aircraft out of service on Friday, after an inspection revealed "pickle fork" cracks, where the fuselage joins the wing of the plane.

A global issue for the American aviation manufacturer, the Federal Aviation Administration in the United States triggered a recommendation for all airlines around the world to immediately check aircraft with more than 30,000 cycles, after several planes were found to have the same issue at the beginning of October.

Examining 33,737 aircraft with more than 22,600 cycles over the past week, Qantas said they will now ground the three defected planes and begin complex repair work.

"As people would expect with Qantas, we've gone above what was required to check our aircraft well ahead of schedule," Chief Executive of Qantas Domestic, Andrew David said.

Although there have been calls from the Australian Licensed Aircraft Engineers Association to ground the entire 75-plane fleet of Qantas 737 aircraft, some experts claim the airline cracks are no cause for concern.

"What is not clearly understood is that all mechanical devices, cars, bridges, ships, aeroplanes etc. all have structural cracks," aircraft designer and senior lecturer in Aerospace Engineering at the University of New South Wales, John Page explained.

"The real question is how design engineers manage these phenomena. In the case of aircraft, the engineer designs the structure to ensure a crack is detected before it becomes critical."

"The significant factor is the rate at which the crack grows, usually this is easy to calculate. If the crack might grow such that it could lead to a catastrophic failure then it has to be remediated before continued operation."

Plagued by controversy over the past year, Boeing's 737 aircraft have been involved in two major aviation disasters.

Believed to be caused by a fault in the model's onboard automation software, 189 people were killed in October 2018 when a Lion Air Flight went down in Indonesia.

In March 2019, 157 also died after an Ethiopian Airlines plane crashed en route to Kenya.

Qantas expect all three grounded aircraft to be back in the air before the end of this year.