New eyewitness video has emerged of Kobe Bryant's helicopter circling "aggressively" 30 minutes before it plunged into a Los Angeles hillside killing the basketball legend, his daughter Gianna and seven others.

The video, posted to Twitter by user @theironlydreams, shows a helicopter believed to be the Sikorsky S-76B that carried the group circling above the Los Angeles suburb of Glendale in foggy weather.

The Today show has confirmed that the Twitter user's home is directly under the helicopter's flight path.

"I try and video /photograph all the weird stuff happening above my house in Glendale, CA," the Twitter user wrote alongside the video.

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"Unfortunately this morning I didn't realise I was filming the helicopter Kobe Bryant, his daughter and others were in 31 minutes before they crashed."

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The eyewitness added in a later tweet that the "pilot was performing a very aggressive circling maneuver, that's why I went outside to Film because it was so loud".

He said he "observed 1 or 2 circles before filming & he was even lower & closer to my house, engine maxed".

The victims

The crash killed LA Lakers legend Bryant and his 13-year-old daughter Gianna.

Kobe Bryant and his daughter Gianna died in the crash, alongside seven others. Photo / Getty
Kobe Bryant and his daughter Gianna died in the crash, alongside seven others. Photo / Getty

It also claimed the life of prominent junior baseball coach John Altobelli, his wife Keri and youngest daughter Alyssa, who played on the same basketball team as Gianna.

Another member of the team, Payton Chester, and her mother Sarah also died, along with Christina Mauser, who coached girls basketball at a nearby private school.

The helicopter pilot, Ara Zobayan, was the final victim and a much loved member of the aviation community, according to friends.

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"Too low"

Aviation veteran Robert Ditchey, who has worked as a pilot and aeronautical engineer, told USA Today that the crash "was totally avoidable".

The site of a helicopter crash that claimed the lives of former NBA great Kobe Bryant, his daughter Gianna and seven others. Photo / Getty
The site of a helicopter crash that claimed the lives of former NBA great Kobe Bryant, his daughter Gianna and seven others. Photo / Getty

"And on the part of some people I can go as far as to say irresponsible," he added.

"Here's one of the most important people in the world who comes to a tragic end like this and you say, 'Why? What the hell happened?'"

The US National Transportation Safety Board (NTSB) has launched a "go team" of up to 18 investigators into the crash that killed the basketball legend amid questions about why the helicopter was flying low in foggy conditions.

Investigators will focus on bad weather and mechanical problems as a potential cause of the tragic crash that has been mourned by basketball fans around the world. Why the helicopter was flying in conditions so foggy that even LA police had grounded their choppers will also likely be raised.

The helicopter circling over Glendale. Photo / Twitter
The helicopter circling over Glendale. Photo / Twitter

Detailed analysis of the flightplan of Bryant's Sikorsky S-76B helicopter, built in 1991, showed it took off just after 9am from John Wayne Airport in Orange County and tracked north over Los Angeles before tacking left towards Thousand Oaks where Bryant's Mamba Sports Centre is based.

Audio from air traffic control reveals the experienced pilot, named as Ara Zobayan, was warned "you're too low" seconds before the helicopter disappeared from radar.

The helicopter's flight path.
The helicopter's flight path.

What exactly happened in the minutes leading up to the crash is unclear, however flightplan analysis published by New York Magazine shows the pilot was flying above hilly terrain and in thick fog, and using "visual flight rules" - or VFR - which means relying on sight rather than instruments to fly.

New York City University aviation professor Paul Cline stressed while he had no direct knowledge of Bryant's incident, fog can quickly turn dangerous when pilots become disorientated.

-Additional reporting, news.com.au