A Boeing 737 modified for use as a waterbomber has been used to fight bushfires for the first time, as the Rural Fire Service battles to save homes in the Newcastle area.

Key points: The Gaia aircraft is a passenger 737 converted to fight fires

The Gaia aircraft is a passenger 737 converted to fight fires It is valued at $7.3 million and can carry more than 15,000 litres of fire retardant

It is valued at $7.3 million and can carry more than 15,000 litres of fire retardant It was used to fight fires for the first time in the world yesterday, in Newcastle

The 737, known as Gaia, dropped several loads on two fires in the Hunter region yesterday, assisting firefighters on the ground.

NSW Rural Fire Service spokesman Chris Garlick said the RFS was pleased with effectiveness of the plane, which can carry more than 15,000 litres of water or fire retardant in a single load.

"It has been tested in other situations to demonstrate its effectiveness, but this is the first time in the world a 737 has been used to fight fires," he said.

"We're stoked with how it went."

Rural Fire crews battle an out of control fire near houses along Lemon Tree Passage Road, in Salt Ash. ( AAP: Darren Pateman )

Gaia is one of four large air tankers being used by the service during this year's bushfire season, and is permanently based in NSW.

The 737 and two fixed-wing scanning aircraft were purchased by the RFS from $26.3 million in funding by the NSW Government to bolster the service's firefighting fleet.

Mr Garlick said different aircraft in the service's firefighting fleet took on different tasks according to their different capabilities.

Due to the size of the aircraft, he said the 737 was particularly useful in laying retardant lines for containment and dropping longer loads.

The Coulson Aviation "Fireliners" are converted passenger aircraft. ( Supplied: Rob Miller/Coulson Group )

It can be used to attack bush and grass fires, create containment lines and provide protection for urban areas.

The 737, which was tested in the US prior to arriving in Australia, is one of six Boeing passenger aircraft converted into air tankers by Canadian company Coulson Aviation.

The aircraft are valued at around $7 million and have the capacity to carry 63 passengers.