A test flight in May over the Potomac River found that the barometric altitude was consistently lower by about 100 feet than the radio and geometric altitudes over the water. The helicopter's barometric altimeter was also obscured during the flight, investigators said.

The army helicopter that crashed into a passenger jet over Washington DC was flying too high, investigators have concluded.

Federal investigators opened a three-day inquiry Wednesday into the January plane crash that killed 67 people over Washington, D. C.