Aviation expert discusses deadly D.C. collision

It is the deadliest U.S. air disaster in nearly 24 years. A team from the NTSB is on the ground near Washington D.C. as they begin what will be a complex investigation into that mid-air collision between a passenger jet and an army helicopter. All 67 people on those two aircraft are believed to be dead. Julianne Fox., a veteran pilot and flight instructor and the principal scientist at Decision Speed joined us on 'The Four' to explain what may have happened.