​Indonesia’s civil aviation authorities have grounded three older Boeing 737NGs, after inspections revealed structural cracks.

Indonesia’s civil aviation authorities have grounded three older Boeing 737NGs, after inspections revealed structural cracks.

Of the three aircraft, two belong to Sriwijaya Air, while the third belongs to Garuda Indonesia, states the Directorate General of Civil Aviation (DGCA).

The move to inspect — and subsequently ground — the popular narrowbody follows a directive by the US Federal Aviation Administration (FAA) for US carriers to inspect their 737NG fleet for cracks.

At the heart of inspections is a piece of hardware known as a "pickle fork", which connects the wing to the fuselage of Boeing 737-800s. Cracking of the hardware could result in structural failure, which affects the structure integrity of the aircraft and result in loss of control.

The order required airlines to inspect 1,911 US-registered 737NGs, including -600, -700, -800 and -900 series aircraft, all of which have clocked more than 30,000 flight cycles.

The FAA has since advised global civil aviation authorities to check inspect their respective airlines’ 737NG fleets.

On 10 October, the Indonesian DGCA issued its airworthiness directive for 737NG inspections. So far, the three aircraft belonging to the two carriers have been found with structural cracks and have been grounded, pending further recommendations by Boeing, says the authority.

Lion Air Group carriers, which include Lion Air and Batik Air, did not have 737NGs with more than 30,000 flight cycles, it adds.

The DGCA also echoed the FAA’s directive in urging Indonesian carriers with 737NGs that have logged between 22,600 and 29,999 cycles to inspect them within the next 1,000 flight cycles.

In an 10 October update, Boeing reported that airlines have found 38 cracks on the global 737NG fleet. It is unclear if Garuda and Sriwijaya were part of this number.

The two carriers join carriers such as Southwest Airlines and Gol in grounding some of their older 737NGs found to have cracks. Southwest has removed two 737NG aircraft from service because of structural cracks discovered during inspections, while Brazil-based Gol grounded 11 aircraft for repair and replacement after completing inspection of its 737NG fleet.

Cirium’s fleets data indicates that there are 213 737NGs operating with Indonesian carriers, comprising 141 737-800s and 72 737-900ERs. The Lion Air Group operates the bulk of the 737NGs, at 116 aircraft.