Three US residents are dead after a water bombing aircraft on contract with the NSW RFS crashed while working on bushfires in the Snowy Monaro.

Premier Gladys Berejiklian confirmed the tragedy on Thursday afternoon, more than three hours after the aircraft lost contact with ground crews and dropped off flight radars at 1.30pm.

The aircraft, a C-130 large air tanker, was spotted after NSW Ambulance and Army helicopters as well as an air force plane joined the search. There are reports the plane burst into flames on impact.

An RFS volunteer, who did not wish to be named, said the plane had been working on the Good Good fire.

"It seems like a tragic accident at this point, none of us are sure about what happened before it crashed," he told The Daily Telegraph.

BOM meteorologist David Wilke said there had been very strong winds and a very turbulent atmosphere near where the plane crash.

"We had turbulence warnings that were out with (very strong wind warnings)," he said.

"I'm not sure what warning we had at the time but there has been significantly turbulent atmosphere."

He said there had been wind gusts of 96kmhr at Bombala and the winds would by faster higher in the air.

Peak View sits south of the Good Good bushfire which has burnt through the Snowy Monaro region during an unprecedented bushfire season.

Conditions have deteriorated for firefighters in southern parts of NSW and the ACT today with high temperatures and strong gusts of wind.

CANBERRA: PIALLIGO AVE

The fire has forced the closure of Canberra Airport as authorities advise residents it is too late to leave.

No planes are arriving or departing after passengers were earlier told flights were delayed by up to three hours as air traffic control gives priority to aerial firefighters.

The fire is travelling in an easterly direction towards Beard, Oaks Estate and West Queanbeyan including Crestwood.

The fire is out of control. Firefighters are on scene. However, under current conditions, the fire is difficult to control.

The fire is one of two burning in the suburb. A second fire on Kallaroo Road in Pialligo is at a watch and act level.

CLYDE MOUNTAIN

The fire has been burning on the southern side of the Kings Highway, in the Deua River Valley.

Fire activity is increasing in the Merricumbene area.

This fire has grown from the Currowan fire on the southern flank.

Despite recent rainfall, a return to hot, dry and windy conditions today is likely to result in an increase in fire activity.

ADAMINABY COMPLEX

Fire activity is increasing.

Strong north-westerly winds are being experienced and the fire is spreading quickly towards the area of Adaminaby.

The fire may reach the Adaminaby area this afternoon.

Areas including Shannons Flat, Ashvale, Anglers Reach, Old Adaminaby and Bobeyan Road may come under threat.

If you are in this area, seek shelter as the fire front approaches.

Protect yourself from the heat of the fire. If you are in nearby areas, monitor conditions. Know what you will do if the fire threatens.

BEGA VALLEY: BIG JACK MOUNTAIN

A fire is burning in the area of Big Jack Mountain and Rocky Hall.

Strong north-westerly winds are being experienced and properties in the area of Mount Durragh, Rocky Hall and Stoves Road may come under threat.

If you in the area of Mount Durragh, Rocky Hall or Wyndham and your plan is to leave or you are not prepared, leave now before it is too late.

Leave only if the path is clear. Leave towards Pambula.

Find rolling updates of the latest fire warnings here.