[Greg McDonald]

From NEWS.COM.AU:

Two people are dead after two planes collided over Sydney's south-west, authorities say.

One plane landed safely but the other plane slammed into a house and burst into flames.

There were people inside the Casula house at the time of the crash but they "were safely evacuated and are being assessed by paramedics at the scene", Ambulance Service of NSW spokeswoman Fiona Cook said.

The plane that hit the house burst into flames, killing two people on board.

"The plane (that hit the house) is on fire," NSW Fire Brigades Superintendent Craig Brierley said, adding that firefighters were at the scene.

A man who witnessed the accident said the plane destroyed the rear of the home on Box Road.

"I was going along the M5 and I've just seen this thing coming down ... the tail was hanging off the back and it's crashed into the back of a house up near Box Road and it's absolutely demolished the back of their house," the man told Fairfax Radio Network.

The second plane, which was also believed to be carrying two people, made its way to Bankstown Airport for an emergency landing, Ms Cook said.

"Reports are it landed safely," she said.

"I believe there were two occupants of that aircraft who are both being assessed."

It was unclear what types of planes were involved.

A Bankstown Airport spokeswoman said the airport was closed for a short time after the second plane landed safely.

She could not say how many people were in the plane or whether any were injured, but said emergency authorities were looking after the male pilot.

"All I can say is he was attended to by ambulance officers and interviewed by police and that's a routine procedure after something like this," she said.

"The airport was closed for a short time to invoke our emergency response plans and the airport is operational at this time."