The US National Transportation Safety Board (NSTB) has issued two safety recommendations for General Electric’s CF6-45/50 aircraft engines to the Federal Aviation Administration (FAA).

The recommendations come in the wake of four recent incidents in which aircraft experienced uncontained engine failures.

An uncontained engine failure occurs when engine failure results in fragments of rotating engine parts penetrating and exiting through the engine case.

According to the NTSB, such an event can cause a direct hazard to an airplane and its passengers as high-energy disk fragments can penetrate the cabin or fuel tanks, damage flight control surfaces, or sever flammable fluid or hydraulic lines.

The first recommendation urges the FAA to insist aircraft equipped with CF6-45/-50s undergo blade borescope inspections at specific intervals up to the time the disk is redesigned.

The second asks the FAA to force GE Aviation to immediately redesign the disk.

Further recommendations ask for another type of inspection and final installation of a redesigned disk into aircraft.