The National Transportation Safety Board provided an update on its investigation into the deadly midair collision near Ronald Reagan Washington National Airport last month, including the potential that there were “bad data” on the Army helicopter.

The Jan. 29 crash between an American Airlines flight from Wichita, Kansas, and an Army helicopter on a routine training mission resulted in all 67 people on both aircraft being killed. The NTSB took over the investigation shortly after the incident and offered its first press conference on the incident in nearly two weeks on Friday.