Crews then located a second aircraft, a Jabiru carrying one man who was pronounced dead at the scene, one kilometre north of the first aircraft.

“Early stages would appear to be a midair collision,” Supt Calman told reporters on Saturday.

“Damage at the scene would indicate the first aircraft has come straight down and we do have witnesses that have reported seeing debris coming from the sky.”

Ambulance and fire crews are at the crash site and two crime scenes have been set up.

The planes were flying in uncontrolled airspace at the time of the accident.

Police believe the Jabiru plane had taken off from the nearby Oaks Airfield.

“The scene that we’re closest to here that has been impacted by fire, it would not have been a survivable impact,” Supt Calman said.

“The second scene that’s a kilometre north of here, that aircraft did not burn, but it would also not have been survivable.”

NSW Ambulance Inspector Joseph Ibrahim said 10 ambulance resources including a helicopter were deployed to the “confronting” scene but “nothing could be done”.

“The nature of the injuries were unsurvivable,” he said.

The sites, covered by bushland, are near two flying schools – Sydney Recreational Flying Club and Dave’s Flying School.

The area is popular with trainee pilots and recreational flyers, local councillor Suzy Brandstater said.

“Recreational flying is very popular and this is probably one of the closest places to Sydney that you can do it,” she told AAP.

The Wollondilly Shire councillor said the accident was a “terrible shock”.

“It’s horrific and I really also feel for community members who saw it,” she said.

“It’s something you’re never going to forget – seeing two planes crash.”

Authorities are urging the public to stay away as forensics and police rescue vehicles move around the area.

The Australian Transport Safety Bureau will deploy a team to the crash sites to interview witnesses and collect air traffic control and flight tracking data, pilot and aircraft maintenance records, and weather information.

“Over coming days, investigators will undertake site mapping, examine the wreckage of both aircraft and recover any relevant components for further examination at the ATSB’s technical facilities in Canberra,” the safety regulator said.

They have urged any witnesses or anyone with footage of the planes in any phase of their flights to contact them.

In Queensland, two people suffered minor injuries on Saturday after a seaplane carrying five people crashed off the coast of Hamilton Island in the Whitsundays.

The occupants were picked up by tour boat operator the Ocean Explorer and taken to shore, where paramedics assessed them.

The bodies of two children have been found following a major search of a bay in southwest Sydney, Australia, hours after a woman was pulled from the waterway.

The trio were seen in distress in Floyd Bay, Lansvale, at about 10.15am on Saturday, NSW police said in a statement.

The woman was located shortly after emergency services arrived but could not be revived.

Authorities initially could not locate the children and undertook an extensive search involving police, the Marine Area Command and the State Emergency Service.

Rescuers were seen combing the waterway on jetskis and in boats.

Ape expert Gen Yamakoshi told the Times the killing isn’t a surprise as the chimpanzees in the area “no longer fear humans”.

“It is not clear if the accidents are as a result of food or excitement’, he told the publication.

“It is similar behaviour to how chimps treat one another. If they are excited they cannot control their behaviour.”

The shock killing angered locals with a violent mob storming the Bossou Environmental Research Institute, a facility that has studied chimps for decades.

The mob brought the baby’s corpse to their door before ransacking and destroying the facility.

They set fire to equipment including drones and computers and destroyed over 200 documents.

It’s the sixth recorded attack on a human from a chimpanzee at the nature reserve this year.

Protester Joseph Doré reportedly told local media the “way she was killed” had “angered the population”.

The chimps’ use of technology to eat food has made them famous, with the group of chimps often seen using stone hammers and anvils to open nuts, the most sophisticated act ever observed of humanity’s genetically closest relative.

Over time the chimps have become boxed in a 16sq km pocket of forest and potentially have been cut off from mates living over the hill.

Villagers and apes ave lived peacefully together for years, but it is feared the chimps’ “over-familiarity” with humans and shrinking forest space has led to an increase in likely attacks.

Yamakoshi, however, said it wasn’t clear whether the attacks are down to food or “excitement”.

There are just seven chimpanzees left in Guinea’s Bossou forest.

In 2022, the oldest member of a chimpanzee tribe, Fana, died in solitude at 71, leaving behind two sons, Foaf and Fanwa.