Wreckage removal under progress: One of the engines among the other wreckage of the American Airlines CRJ700 aircraft (N709PS) has been recovered from the water of the Potomac River on Monday.

National Transportation Safety Board has said that black box (Flight Data Recorder) data indicates the aircraft was flying at around 325 feet at the time of collision. That altitude is well higher than the 200 feet set by the Federal Aviation Administration for helicopter traffic in that area.