“… Data from the jet’s flight recorder showed its altitude as 325 feet (99 meters), plus or minus 25 feet (7.6 meters), when the crash happened Wednesday night, National Transportation Safety Board officials told reporters. Data in the control tower, though, showed the Black Hawk helicopter at 200 feet (61 meters) at the time.
The roughly 100-foot (30-meter) discrepancy has yet to be explained.
Investigators hope to reconcile the altitude differences with data from the helicopter’s black box, which is taking more time to retrieve because it became waterlogged after it plunged into the Potomac River. They also said they plan to refine the tower data, which can be less reliable. …”