The European Union Aviation Safety Agency issued a warning about the London-based supplier of distributing "suspected unapproved parts" in August, with Virgin, Southwest and, most recently, United, having since identified the suspected parts. AOG Technics was reported to have used false documentation for the engine parts, which are of unknown origin, according to the European Union Aviation Safety Agency.
Bloomberg previously reported that the suspicious engine parts were used for repairs of CFM56 engines, which are used on many Airbus A320 and Boeing 737 commercial aircrafts, resulting in the popular airlines having to search through records for references to AOG Technics. The total number of suspected spare parts supplied to the three airlines has not yet been determined.
A United Airlines spokesperson told Insider that the discovery was made in a single engine on each of two aircrafts, which included one that was already undergoing maintenance at the time.
"We are replacing the affected engines on both aircraft before they are returned to service, and we'll continue to investigate as new information becomes available from our suppliers," the spokesperson said.
United Airlines had previously issued a ground stop for all flights nationwide due to an "equipment outage" earlier this month, ABC News reported on September 5.