The National Transportation Safety Board will question witnesses Thursday about air traffic control training, a key part of the investigation into January’s deadly midair collision at Ronald Reagan Washington National Airport.

Investigators testifying at a hearing into the January's mid-air crash in Washington DC suggest faulty altitude data may have led to a miscalculation.

The head of the National Transportation Safety Board sharply criticized U.S. officials for failing to act before the January 29 collision of a U.S. Army helicopter with an American Airlines regional jet in Washington that killed 67 people.