{"as_of":"2026-11-02","attribution":"FAA and NTSB data via eFlight Registry (https://eflight.com)","connections":[{"group":"Applies to","items":[{"count":7,"name":"Douglas DC-9","note":"","unit":"registered","url":"https://eflight.com/models/douglas/dc-9#airworthiness"},{"count":10,"name":"Mcdonnell Douglas Aircraft Co MD-88","note":"","unit":"registered","url":"https://eflight.com/models/mcdonnell-douglas-aircraft-co/md-88#airworthiness"},{"count":93,"name":"Mcdonnell Douglas DC-9","note":"","unit":"registered","url":"https://eflight.com/models/mcdonnell-douglas/dc-9#airworthiness"}],"relation":"applies to"},{"group":"System","items":[{"count":null,"name":"Other and general","note":"","unit":"","url":"https://eflight.com/systems/other"}],"relation":"about"},{"group":"Related orders","items":[{"count":null,"name":"Replaced by 99-21-06","note":"","unit":"","url":"https://eflight.com/directives/99-21-06"}],"relation":"related to"},{"group":"More","items":[{"count":null,"name":"Every FAA order","note":"","unit":"","url":"https://eflight.com/directives"},{"count":null,"name":"Every aircraft system","note":"","unit":"","url":"https://eflight.com/systems"}],"relation":"see also"}],"graph":"https://eflight.com/graph","graph_index":"https://eflight.com/graph/index.json","license":"https://creativecommons.org/licenses/by/4.0/","node":{"effective":"1991-10-30","faa_document":"https://drs.faa.gov/browse/excelExternalWindow/EA68B46B77EA94D186256A1C0076168D.0001","id":"91-21-11","kind":"AD","name":"Airworthiness directive 91-21-11","published":"","subject":"Slat Drive Mechanism Brackets","system":"other","type":"directive","url":"https://eflight.com/directives/91-21-11"},"source":"FAA Civil Aviation Registry, FAA airport file, NTSB accident database; assembled by eFlight Registry"}