NTSB definitions

Ntsb

1) Accident investigation agcy 2) Accident investigation gp 3) Accident investigation grp 4) Accident investigation org 5) Accident-investigating agcy 6) Accident-investigating org 7) Accident-probing agcy 8) Accident-probing org 9) Airline investigative org 10) Crash investigation org 11) Crash scene org
Found on https://www.crosswordclues.com/clue/ntsb

NTSB

National Transportation Safety Board. A United States government organisation in charge of investigating in the case of an accident. In many countries, an AAIB fulfills that role.
Found on http://airodyssey.net/reference/glossary/

ntsb

National Transportation Safety Board; investigates accidents and other incidents related to public transportation
Found on http://www.ddtvl.com/glossary/glossary.htm