Kobe Bryant and eight others, which

crashed near Los Angeles.

It's a common route, spanning an area well-traveled

by aircraft every day.

So we wanted to understand how, despite this, such

an accident could occur.

Using a chartered helicopter, flight tracking data

and images from the day, we've re-traced the flight path

to examine the conditions that may have led to the crash.

The helicopter took off from John Wayne Airport

in Orange County.

Its destination, another airport

near the sports academy, which Bryant owned.

The first half of the flight is uneventful.

The terrain, here in the Los Angeles basin, is flat.

That makes it relatively easy to navigate, even

in overcast weather.

Bryant, himself, made the trip routinely.

On the day of the crash, the weather in this area is fine.

There's four miles visibility.

Within 13 minutes, the helicopter

passes by downtown Los Angeles,

passes Dodger Stadium and begins

to enter the San Fernando Valley.

The terrain begins to rise.

That day, air controllers tell Bryant's pilot

to stay in a holding pattern over the city of Glendale.

They circle for more than 10 minutes,

as other air traffic is cleared.

It's around this time that a retired pilot on the ground

happens to film the helicopter overhead.

We can see in the footage that the sky

is considerably overcast.

The pilot received special clearance

to continue on in the low-visibility weather …

… and flies into the San Fernando Valley,

following the freeway system along the edge

of the foothills.

We can see the densely populated terrain is still

low and flat.

The weather for our chartered flight is clear,

but images from the day of Bryant's flight

show that visibility has become extremely limited.

One reason: If we pause and pull up,

we can see that the Pacific Ocean is just

on the other side of these hills.

Cold, moist air coming off the water,

and hitting the mountains, can quickly

form thick and low cloud cover.

With a lower ceiling and higher mountainous terrain,

there's now a much smaller path to safely fly.

Roughly three minutes before the crash,

the helicopter begins flying along Highway 101.

It's a common route.

The highway is a distinct landmark

that's easy to follow, and it runs

through a low point in the foothills,

making it easier for pilots to stay below cloud cover.

Bryant's pilot had requested “flight following,”

where controllers track an aircraft to help the pilot

during rough conditions.

Just before the crash, the ground controller

tells the pilot he's too low for tracking.

The pilot radios that he's climbing

to avoid the cloud layer.

The helicopter quickly gains altitude.

At about 2,300 feet, it turns away from Highway 101,

and crashes into the side of a hill.

The debris field is around 500 feet long.

Investigators said that the helicopter

may have missed clearing the top of the hill

by 20 to 30 feet.

They still haven't determined a cause for the crash.