An eyewitness believes he has captured the moment Kobe Bryant's helicopter was circling over Glendale, California, just 30 minutes before the deadly crash as aviation experts question why the chopper was flying in the foggy weather in the first place.

'I try and video /photograph all the weird stuff happening above my house in Glendale,CA,' a Twitter user with the handle @theironlydreams wrote.

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

According to a tweet from the same user on Monday, the 'pilot was performing a very aggressive circling maneuver, that’s why I went outside to Film because it was so loud'.

An eyewitness believes he has captured the moment Kobe Bryant's helicopter was circling over Glendale, California, just 30 minutes before the deadly crash

According to the Today show, the man's home has been verified as being under the flight path of the Sikorsky S-76B chopper

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

According to the Today show, the man's home has been verified as being under the flight path of the Sikorsky S-76B chopper.

Bryant, 41, and his daughter, Gianna, 13, were both killed in the crash.

Also killed were John Altobelli, 56, longtime head coach of Southern California's Orange Coast College baseball team; his wife, Keri; and daughter, Alyssa, who played on the same basketball team as Bryant's daughter; and Christina Mauser, a girls' basketball coach at a Southern California elementary school.

Another young player, Payton Chester, was also killed in the crash along with her mother Sarah Chester.

The pilot, Ara Zobayan, 50, was the ninth victim. He was the chief pilot for the aircraft's owner, Island Express Helicopters. The company said the pilot had more than 10 years of experience and had logged more than 8,000 flight hours.

He also was a flight instructor who had flown Bryant and other celebrities several times before.

Zobayan was instrument-rated, which means he was qualified to fly in fog.

The pilot, Ara Zobayan (left and right), 50, was the chief pilot for the aircraft's owner, Island Express Helicopters. The company said the pilot had more than 10 years experience and had logged more than 8,000 flight hours

Dramatic pictures have revealed how Bryant's helicopter exploded into a fireball after it plunged 1,000 feet into a hillside on Sunday, killing the NBA legend and eight others

His helicopter left Santa Ana in Orange County, south of Los Angeles, shortly after 9am on Sunday, a time when conditions were not suitable for flying, according to the Los Angeles Police Department. Investigators at the crash site on Monday

Investigators work at the scene of the helicopter crash which killed Bryant in Calabasas, California, on Monday

The weather was so foggy when the helicopter took off that the Los Angeles Police Department and the county sheriff's department had grounded their own choppers. Investigators collecting evidence from the scene on Monday

A firetruck arrives to the scene of the Sunday morning helicopter crash in Calabasas, California

The chartered Sikorsky S-76B was a luxury twin-engine aircraft often used by Bryant in traffic-jumping hops around the LA area's notoriously congested sprawl

But even experienced pilots may have only seconds to act when they are blinded by weather, an expert said as investigators began scouring the wreckage for clues to Sunday morning's crash.

Robert Ditchey, a veteran airplane pilot, aeronautical engineer and former airline executive, told USA Today that the crash 'was totally avoidable'.

'And on the part of some people I can go as far as to say irresponsible,' Ditchey 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?"'

Bryant's helicopter left Santa Ana in Orange County, south of Los Angeles, shortly after 9am on Sunday, a time when conditions were not suitable for flying, according to the Los Angeles Police Department.

There was an overcast at 1,300 feet and visibility of about five miles. Zobayan was initially flying under VFR, meaning that he was relying on his ability to see the terrain below him.

The weather was so foggy that the Los Angeles Police Department and the county sheriff's department had grounded their own choppers.

Bryant, 41, and his daughter, Gianna (both pictured), 13, were killed in the crash

Among those killed in the crash were John Altobelli (left), 56, longtime head coach of Southern California's Orange Coast College baseball team; his wife, Keri (left, with John); and daughter, Alyssa (right), who played on the same basketball team as Bryant's daughter

Another young player, Payton Chester (left), was also killed in the crash along with her mother Sarah Chester (right)

Christina Mauser (pictured with her husband, who was not on the chopper), a girls' basketball coach at a Southern California elementary school, was also killed

Ditchey questioned why anybody would hop on a helicopter in what he called 'very scary conditions'.

'The weather is not good enough for the police to fly,' Ditchey told USA Today. 'Why should Kobe do it?'

Around 9.20am, the helicopter circled for about 15 minutes just east of Interstate 5, near Glendale. Air traffic controllers held up the helicopter for other aircraft for about 11 minutes, before clearing the Sikorsky S-76 to proceed north along Interstate 5 through Burbank's airspace.

It was revealed on Monday that Zobayan was given a special clearance to fly under worse than normal weather conditions.

In audio captured by LiveATC.net Zobayan is heard requesting to fly under special visual flight rules (SVFR).

Zobayan was told to follow a freeway and stay at or below 2,500 feet, according to radio traffic.

'Maintain special VFR at or below 2,500,' the pilot is heard confirming to the controller at Burbank Airport.

A Federal Aviation Administration (FAA) official noted a pilot 'does not get a general, or blanket, clearance from the FAA to fly in these conditions. A pilot is responsible for determining whether it is safe to fly in current and expected conditions'.

Fans gather near a makeshift memorial to the mourn the death of Bryant at LA Live plaza in front of Staples Center in Los Angeles on Monday

A fan wearing a Lakers hat holds his head in his hands while visiting a memorial for Bryant near Staples Center on Monday

A man writes a message on the pavement near a makeshift memorial as fans gather to mourn the death of Bryant at LA Live plaza in front of Staples Center in Los Angeles on Monday

Mourners gather at a memorial for Bryant near Staples Center in Los Angeles on Monday

People gather in front of a mural in honor of Bryant and his daughter Gianna in Los Angeles, California

Under an SVFR clearance, pilots are allowed to fly in weather conditions worse than those allowed for visual flight rules (VFR). Special VFR clearances are only issued when cloud ceilings are below 1,000 feet above ground level.

Flying that low to the ground can be very disorienting and risky, and it's possible that the pilot became disoriented due to the visibility conditions when the helicopter appeared to veer off its path above US Route 101.

Air traffic controllers noted poor visibility around Burbank, just to the north, and Van Nuys, to the northwest. Due to the poor visibility, the pilot could have contacted air traffic controllers and requested to switch to instrument flight rules (IFR), which would have allowed him to navigate through the clouds.

However, when pilots fly under IFR, it can take up a lot of time, especially in Southern California, which has an extremely busy airspace.

Experts believe the pilot may have become confused in the fog and went into a fatal dive Sunday's weather conditions continued to worsen as Ara Zobayan piloted the Sikorsky S-76B that was carrying Kobe Bryant, his 13-year-old daughter and six other passengers. It was already a foggy day and the Los Angeles Police Department grounded their choppers due to the conditions. Zobayan decided to fly under visual flight rules (VFR), which meant he was relying on his eyes to avoid obstacles. But visibility began to decrease even more as he approached Glendale where he circled for about 15 minutes while waiting for air traffic control clearance. He maintained an altitude of 750ft and speed of 72mph. Once he was cleared to head over Burbank, Zobayan began to climb and accelerate. He maintained an altitude of 800ft and speed of 148mph. While following US Route 101 up to Northridge, he continued his climb under special visual flight rules. He maintained an altitude of 1,400ft and speed of 160mph. The pilot continued to climb; however he reduced his speed as he approached Calabasas. Experts believe this may have been a point where he attempted to avoid an obstacle. He climbed to an altitude of 2,000ft and slowed to 152mph. It's also believed that the pilot may have been going too fast. Even at 120mph, that would’ve only given the pilot 30 seconds to avoid a mountain range, experts say. Experts have said that the pilot’s high speed could've meant that he was 'completely out of control’ and turned off course. It’s believed that the pilot got confused in the fog and went into a fatal dive at 500 feet in 15 seconds. The aircraft was on its way to Camarillo Airport in Ventura County and from there Bryant and the passengers were supposed to attend a tournament at the NBA star's Mamba Sports Academy. Advertisement

Pilots flying under IFR will have to begin 20 miles or more away from the runway and are required to use special instructions in the form of diagrams called approach plates in order to land

The aircraft continued under special VFR and around 9.40am it turned west to follow US Route 101, the Ventura Highway.

A short time later, the helicopter turned again, toward the southeast, and climbed to more than 2,000 feet, in what appeared to be an attempt to put some space between the helicopter and the high terrain.

In air traffic control audio, the pilot is told by a controller that 'you're still too low level' to be tracked by radar.

This did not appear to be a sign of distress, because the helicopter was actually ascending at the time and the controller was referring to the technical difficulty with reading data rather than warning of an imminent crash.

About four minutes later, 'the pilot advised they were climbing to avoid a cloud layer,' Jennifer Homendy of the National Transportation Safety Board (NTSB) said Monday.

It was his last message to air traffic controllers.

'When ATC asked what the pilot planned to do, there was no reply,' Homendy said.

'Radar data indicates the helicopter climbed to 2,300 feet and then began a left descending turn.'

Two minutes later, someone on the ground called 911 to report the crash. The helicopter had slammed into a hillside and burst into flames.

Details of what followed are still under investigation but there are indications that the helicopter plunged some 1,000 feet.

It was flying at about 184mph and descending at a rate of more than 4,000 feet per minute when it struck the ground, according to data from Flightradar24.

Ditchey told USA Today that helicopters can operate in bad weather because they can fly low, but they need to have reasonable visibility of at least one mile.

According to Ditchey, even then, going at 120mph only gives the pilot only 30 seconds to avoid a large obstacle, suggesting the pilot may have been traveling too fast to properly maneuver around obstacles.

Ditchey said the helicopter appeared to run into trouble around the Glendale area where visibility decreased.

'They’re in the fog, and you’re down hugging the ground trying to fly up the highway and barely able to see it,' Ditchey told the news outlet.

Jennifer Homendy (center) of the National Transportation Safety Board (NTSB) said Monday that NTSB is expected to be on the scene for five days. 'It was a pretty devastating accident scene,' she said of the widespread wreckage

Federal investigators leave a news conference about the crash that killed Bryant. NTSB investigators scoured the crash site to collect evidence

'He's down only 100 feet or so above the ground. In that area of the San Fernando Valley you have mountains on either side of you … and the clouds have obscured them, and you don’t have that much room to maneuver.'

The chartered Sikorsky S-76B was a luxury twin-engine aircraft often used by Bryant in traffic-jumping hops around the LA area's notoriously congested sprawl.

It was heading from John Wayne Airport in Orange County to Camarillo Airport in Ventura County when it crashed in Calabasas.

Bryant, his daughter, Gianna, and the other passengers were heading to the NBA great's Mamba Sports Academy, a youth sports center in Thousand Oaks.

He was to coach a basketball tournament there in which his daughter was supposed to play.

Bryant's death was mourned around the world in an outpouring of shocked grief.

'Words can't describe the pain I am feeling. I loved Kobe — he was like a little brother to me,' retired NBA great Michael Jordan said. 'We used to talk often, and I will miss those conversations very much. He was a fierce competitor, one of the greats of the game and a creative force.'

Bryant retired in 2016 as the third-leading scorer in NBA history, finishing two decades with the Lakers as a prolific shot-maker with a sublime all-around game and a relentless competitive ethic.

He held that spot in the league scoring ranks until Saturday night, when the Lakers' LeBron James passed him for third place during a game in Philadelphia, Bryant's hometown.

'You have road trips and times where you don't see your kids so every chance I get to see them and spend time with them... I want that,' Bryant said in the interview. Bryant is seen with his wife, Vanessa, and three of their children

Bryant retired in 2016 as the third-leading scorer in NBA history, finishing two decades with the Lakers as a prolific shot-maker with a sublime all-around game and a relentless competitive ethic

James wept on the tarmac at Los Angeles International Airport yesterday after the Lakers learned on a flight home that their former teammate had died.

The NBA kept its games on as scheduled when the news broke, but the San Antonio Spurs and Toronto Raptors both took voluntary 24-second shot clock violations at the start of their game in honor of Bryant, who wore No. 24 for the second half of his career.

During the Grammy Awards, Lizzo said 'tonight is for Kobe!' after host Alicia Keys paid tribute, telling those gathered for the ceremony: 'We're literally standing here, heartbroken, in the house that Kobe Bryant built.'

His longtime Lakers teammate Shaquille O'Neal wrote on Twitter: 'There's no words to express the pain I'm going through now with this tragic and sad moment of loosing my friend, my brother, my partner in winning championships, my dude and my homie.

'I love you brother and you will be missed. My condolences goes out to the Bryant family and the families of the other passengers on board. IM SICK RIGHT NOW!'

Bryant teamed with Shaquille O'Neal in a combustible partnership to lead the Lakers to consecutive NBA titles in 2000, 2001 and 2002.

Retired NBA superstar Michael Jordan, to whom Bryant was often compared, expressed similar sentiments.

'Words can't describe the pain I am feeling. I loved Kobe — he was like a little brother to me,' Jordan said in a statement. 'We used to talk often, and I will miss those conversations very much. He was a fierce competitor, one of the greats of the game and a creative force.'

Former Lakers star Magic Johnson tweeted: 'Laker Nation, the game of basketball and our city, will never be the same without Kobe.'

Bryant was the league MVP in 2008 and a two-time NBA scoring champion, and he earned 12 selections to the NBA's All-Defensive teams.

He went on to win two more titles in 2009 and 2010, and retired in 2016.

Kobe and Gianna are survived by his wife Vanessa and their three other daughters - Natalia, Bianka and Capri, who was born last summer.