Investigators from the National Transportation Safety Commission conducted their first briefing on camera in nearly two weeks since the air collision on January 29. Both planes crashed into the Potomac River, killing all 67 people on both planes.

NTSB chairman Jennifer Homendy said the collision between the helicopter and the "CRJ" aircraft occurred 278 feet by the river. The helicopter shouldn't be more than 200 feet.

However, HOPENEDY said it is not clear whether the altimeter in the helicopter shows the pilot the appropriate height above the ground. Investigators are "seeing conflicting information in the data" and are continuing to conduct analysis, she said.

Some of the radio transmissions between the Air Traffic Controller and the Blackhawks were also not fully heard by the helicopter pilots, Homdi said.

She said there was at least one transmission - when the controller told the helicopter to "pass behind the CRJ", the 17 seconds before the impact might not have been received by the Blackhawk. That's because the helicopter crew is already making radio transmissions and part of what the controller says is "step on."

The crew of the American Airlines regional jet saw the helicopter about a second or two before the crash. Homdi said the pilot of the plane pulled the plane's nose completely to nine degrees before the impact. She said the helicopter crew continued to fly in the same direction and speed until the collision.

She said helicopter staff appeared to be wearing night vision goggles, which was limited in the view the pilot could see. She said the NTSB planned a complete visual simulation to understand everything the Black Hawk pilots could witness before the accident.

The complete survey of NTSB is expected to take at least one year.