London CNN Business  — 

Ryanair is the latest major Boeing customer to find cracks in some of its 737s.

The Irish airline said in a statement Wednesday that inspections ordered by US regulators had turned up problems with a small number of its oldest 737s, which are now being repaired by Boeing.

The US Federal Aviation Administration ordered inspections of Boeing 737 NG, or Next Generation, aircraft in September after the company said structural cracks had been found on heavily used planes.

The cracks were found on what is known as the “pickle fork,” which helps attach the wings to the aircraft.

The cracking issue is the latest blow to Boeing (BA). All 737 Max jets, a newer version of the aircraft, have been grounded since March following two fatal crashes that killed 346 crew and passengers.

Ryanair (RYAAY) said Wednesday it has inspected more than 70 of its oldest 737 NG planes, discovering issues with an unspecified “tiny number” of them.

The Guardian, which was first to report the news, said that cracks had been found on at least three Ryanair planes. Europe’s biggest low-cost carrier operates a fleet of 455 Boeing 737 aircraft.

Ryanair said it’s now inspecting younger aircraft, and has not found “any further issues.” The carrier added it’s confident the issue will not affect its flight schedules.

There are about 6,800 of the 737 NG jets in service around the world. Boeing said Wednesday that more than 1,100 of them have been inspected, and less than 5% have cracks.

All 737 NG planes with over 30,000 flight cycles have been inspected, according to Boeing. The FAA’s October directive gave airlines a year to inspect jets with at least 22,600 flights.

According to the Irish Aviation Authority, all operators in the country have completed the required inspections. “If any cracks are found, the aircraft must be repaired before further flight,” the IAA said in an emailed statement.

Last week, Australian airline Qantas pulled three 737 NG planes from service after they were found to have cracking. The head of Qantas Engineering, Chris Snook, said that cracks did not immediately compromise safety.

Southwest (LUV) and Brazilian carrier Gol are also among the airlines that have grounded planes over the cracking issue.

Boeing said in a recent statement that safety and quality are its top priorities.

“Boeing regrets the impact this issue is having on our customers worldwide,” said the aircraft maker. “We are working around the clock to provide the support needed to return all airplanes to service as soon as possible.”

-— Chris Isidore, Jack Guy and Carly Walsh contributed to this report.