"It is unconscionable that the FAA permits unregulated flights in a crowded airspace in a major metropolitan area," Nadler said. "And it is ridiculous that private planes and helicopters flying through a crowded area are dependent, while in flight, on visually sighting other aircraft and communicating with them. The real-life repercussions of these non-existent regulations have been disastrous."
City Council Speaker Christine C. Quinn said her office would hold hearings on the issue.
"Regardless of what the investigation uncovers, the time has come for the FAA to reassess their regulatory practices for the Hudson River corridor," Quinn said. "And it's time for the City to review and analyze our policies when it comes to air traffic over our neighborhoods."
"I'm not going to pressure the FAA," Mayor Michael Bloomberg said Monday. "They don't need me weighing in. They know certainly well what goes on there. They are professionals. I assume they're going to wait until the National Transportation Safety Board to make its report and then they'll make their decisions."
"We'll have to wait and see if Safety Board finds any issue," Hersman said on "Good Morning America". "Have to see what facts show us."
ABC News aviation consultant John Nance said blind spots could have played a role in this accident, but it's too soon to tell what happened in this case.
"We shouldn't rush to any blame because the problem is really societal," Nance said on "GMA." "We've been engaging in aviation mythology, see and avoid for a long time."
"There are blind spots just about everywhere," he added. "We don't have that much visual range and very easy for two planes to approach each other and neither see anything."
Nance, too, said there should be more clear-cut guidelines and technology to keep planes and tour helicopters safe, rather than having pilots adopt the "see and avoid" approach in blind zones.
"It's time we move on from that concept and use electronics and procedures to bridge the gap," Nance said. "What we have now is inadequate."
"This is nowhere near the type of safety that we've been able to create in aviation in other areas and we need to get it up to that level," he said.
NTSB records show Liberty Helicopters has had eight previous accidents and one "incident" since 1995 with no fatalities, Hersman said. Two accidents and an incident were reported last year.
She also said midair collisions -- 11 per year in the last decade -- have resulted in 158 deaths.
"One midair a year is too many, and the Board has seen 11 midairs a year for the last decade," Hersman said. "And so we are really very concerned about what kind of procedures, technologies, training, might be available to prevent these kinds of accidents."
"Certainly there is a common theme of people not being aware of each other," she also said.
Meantime, victims' families continue to mourn their loved ones. Accompanying Altman on the Piper were his brother and nephew. The helicopter was being flown by a 32-year-old pilot -- Jeremy Clark of Lanoka Harbor, N.J. -- and five Italian tourists, including a couple and their teenager, and a father and son, whose mother stayed behind because she was too nervous to climb on board.
ABC News' Richard Esposito, Huma Khan and Kate Barrett contributed to this report.