HONOLULU -- A preliminary investigation into a tour helicopter crash on Kauai shows a major discrepancy in what happened.

Three people died in the September crash, three others survived. The chopper was on a 45-minute aerial tour of the Garden Isle.

The pilot said he was attempting to avoid another helicopter before his chopper lost airspeed, rapidly descended and crashed into the ocean.

The pilot told the National Transportation Safety Board investigators that he "suddenly saw a MD500 coming straight for me." He told investigators that he turned left to avoid the aircraft.

After that, the pilot, Glen Lampton, 43, said he tried to fly around heavy rain in the area. That's when Lampton said the helicopter lost airspeed and plunged. Before hitting the water the pilot said he was able to get a burst of power to get the aircraft into the air slightly.

The NTSB interviewed other tour operators and so far has found no other helicopters that could have interfered with the chopper that crashed.

The final investigation could take more than a year.