More than 90% percent of certification work on new aircraft and aircraft parts is outsourced by the FAA to the manufacturers themselves, according to a GAO report. Similar to the FAA delegation of airman certification authority to Designated Pilot Examiners, the FAA has been authorizing most certification work to be performed by employees of the manufacturers themselves through the Organization Designation Authorization (ODA) program.
Source: avwebFAA Doesn't Do Most Aircraft Certification Work