Comment by yellow_lead

> Delta would not say if the engines with the fraudulently documented parts had been on planes while they were in service.

If they weren't, Delta would say so, since it makes them look better. That they won't say means the parts were used in service.

> None of Delta’s aircraft are currently flying with unapproved parts, and the discovery hasn’t affected flight operations

How do they know? Even these fake parts were not detected by Delta but "were detected during engine work by an unnamed third party."