Ben Lane warned fellow helicopter pilot Jeremy Clarke on Saturday that the plane was bearing down on him.
Lane tells the Daily News that another pilot heard him scream "Watch out! Watch out!"
He doesn't remember screaming. But he does recall seeing a wing and chopper blades falling before both aircraft plummeted, killing nine.
He searched for survivors, but there were none.
The National Transportation Safety Board (NTSB) is investigating Saturday's accident. NTSB Chairman Deborah Hersman told CBS' "The Early Show" Anchor Harry Smith Monday morning that the agency tasked with investigating every civil aviation accident in the U.S. isn't laying blame until it completes its investigation.
"We know that there is a lot of traffic over the Hudson," Hersman said. "We don't know all of the facts. We've only been here a day, and so we won't be reaching any conclusions" at this time.
"This accident is a tragedy," Hersman said. "Unfortunately the NTSB sees about 11 mid-air collisions every year."
Lane says a crash was inevitable along the busy corridor. He says helicopter pilots stay in constant radio contact. But many small plane pilots - he calls them "weekend warriors" - do not.
"I don't care if they are life-long pilots, 90 percent of the time they don't make a radio call," Lane told the Daily News. "We were borderline surprised that it took so long for a crash like this to happen."
A chief investigator says divers hope to pull the plane that crashed into Clarke's helicopter out of the Hudson River on Monday. But their first priority is to recover the two remaining victims of the midair crash that killed nine people.
An Army Corps of Engineers crane lifted the twisted wreckage of the helicopter from 30 feet of water on Sunday. It's believed the plane is nearby, about 50 feet deep.