"30 enemy aircraft over the Channel flying due West!"

It would become one of the most significant battles of the Second World War.

Advancing through Europe, Nazi Germany set its sights on the British Isles.

"Phase one, knock out the Royal Air Force and it's bases, get control of the air and

the sea lanes across the Channel"

Outnumbered and outgunned, it looked like British fighters wouldn't stand a chance

against the superior Luftwaffe.

But they had a technology that would give them an edge...

Here's How Britain's Hunt For A Death Ray Gave Us Radar

In 2017, something incredible happened.

Not a single passenger jet was involved in a fatal accident, despite a record four billion

air passenger journeys being made.

The skies had never been so busy - but 2017 was the safest year in commercial aviation.

In fact, you're much more at risk on the way to the airport.

According to a Harvard study, the odds of being killed in a car crash are 1 in 5000.

Your odds of death in a plane crash are 1 in 11 million.

How aircraft avoid mid-air collisions is thanks to radar.

But it all started with the search for a deadly weapon.

Roll back to 1935.

War was looming and there were rumours Germany had something capable of wiping out whole towns

The British Government feared an aerial invasion and wanted a 'death ray' that could knock

German planes out of the sky.

The Air Ministry approached electrical engineer, Robert Watson-Watt.

Watson-Watt had worked for the Meteorological Office where he experimented using radio waves

to locate thunderstorms.

He quickly determined a death ray was practically impossible to build.

But leaning on their previous work in firing radio waves at targets,

they offered an alternative to the death ray.

His memo to the Ministry was titled "The Detection of Aircraft by Radio Methods"

Two weeks later, the team successfully used a radio transmitter to detect a circling RAF

bomber 8 miles away.

Radio detection and ranging - radar - was born.

The team quickly extended the range of radar up to 100 miles.

They worked fast - the fear of imminent attack was never far from their minds.

By the outbreak of war in 1939 the team had built 19 radar stations on Britain's south and

east coasts, with over 50 built by 1945.

This system of stations became known as 'Chain Home'; as well as detecting enemy aircraft,

it centralized radar reports to operators who could quickly scramble fighter crews to

intercept the enemy.

Teams from Germany, Japan and the U.S. were all working on their own radar systems'

but the U.K.'s was the most advanced.

British scientists developed something called a 'cavity magnetron'

improving on a German idea - and then shared it with allies in the U.S.

The technology reduced the size of radar devices meaning they could be installed in night-fighters,

anti-submarine aircraft and escort ships.

Planes were given transponders - devices that send and receive radio signals - which would

help them identify enemy and friendly planes, increasingly useful when visibility was poor.

But radar could only do so much.

"The Nazis struck Britain with all their might.

They levelled thousands upon thousands of homes and damaged millions of others.

They killed more than 40,000 men, women and children."

Without radar, it might have been much worse.

The Nazis never landed on British soil.

After the war, air travel exploded, especially in the U.S.

"Many other war-tested devices are incorporated in the luxury airliner which ushers in a new

era in American aviation"

But there were few regulations and many airports didn't even install radar

"See And Be Seen" was the main rule of thumb.

That would quickly change after June 30 1956.

128 people died following a collision between two airlines over the Grand Canyon.

Investigators determined the pilots could not see each other due to cloudy conditions.

As the public learned of the crude nature of air traffic control, pressure mounted on

Congress to make air travel safer.

A year later President Eisenhower signed the Airways Modernization Act, which improved

monitoring of planes from takeoff to landing.

Using transponders based on those developed during the Battle of Britain, US airlines

devised a compulsory system that would become industry-standard known as TCAS -

the Traffic Alert and Collision Avoidance System.

If a plane entered another's air space, it would automatically issue a command to manoeuvre.

CLIMB CLIMB,

DESCEND, DESCEND

Today, radar systems work in conjunction to paint a complete and detailed picture of the

skies, using transponders to identify planes, their positions and their altitude.

Air traffic control on the ground tracks speed and direction by monitoring transmissions.

"As the controllers say, 'the best way to fly is in radar contact'"

GPS has been added to the equation too because once an aircraft is out at sea, radar coverage fades.

Planes can now fly for hours with precise navigation.

So events like the disappearance of Malaysian Airways flight MH370 in 2014 undoubtedly add

to the fears we have of flying,

but when looked at in context, such accidents are extremely rare thanks to the giant leaps

made in safety, galvanised all those years ago by the Battle of Britain.