Commercial Space Transportation Safety Act of 2019 This bill authorizes the National Transportation Safety Board (NTSB) to investigate a commercial space transportation accident in which there is (1) a known impact of a commercial launch vehicle, the payload of such vehicle, or any component thereof outside of the hazard area designated for the launch or reentry of such vehicle; (2) a fatality or significant injury of any individual, regardless of whether the individual was on board the commercial launch vehicle at the time of the accident; or (3) substantial damage to property that is not associated with commercial space launch activities and that is not located at the launch site. The NTSB shall seek to enter into a memorandum of understanding with any government agency with the authority to certify a commercial space transportation operation to delineate the conditions under which a commercial space transportation accident will be investigated by such agency rather than by the NTSB.