Congress will hold a hearing Thursday morning about what we know so far about the deadly midair collision above the nation's capital that killed 67 people in January and what might have caused it. The head of the National Transportation Safety Board that is investigating the crash will appear along with the leaders of the Federal Aviation Administration and the Army's aviation division to answer questions in the Senate.

The acting FAA chief and others faced questions from senators following the midair collision in January that took 67 lives.