Thousands of passengers have begun their journey home from Darwin after a volcanic ash cloud over the Top End grounded planes yesterday.

Flights in and out of Darwin airport resumed this afternoon after the Sangeang Api volcano, located off the north-east coast of Sumbawa, began erupting on Friday night.

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The plume of ash spread over the Kimberley and the Top End forcing airlines to cancel most flights in and out of Darwin on Saturday and early Sunday.

Thirty-one flights were cancelled, creating a backlog of thousands of people. Jetstar says about 2,000 of their customers were affected.

In Perth, airline passengers hoping to travel to Bali were also hit with flight cancellations.

This morning the Volcanic Ash Advisory Centre (VAAC) briefed the airlines, saying a strong trough in the atmosphere was helping the ash dissipate.

"It is thinning out both horizontally and vertically in the atmosphere so its concentration is weakening," a spokesman for VAAC said.

"We still expect there to be some ash extending over the north of the Northern Territory and the far northern Kimberley but this is expected to dissipate during today."

Regional airline Air North was advising customers to check with the airline.

Flights from Kununurra Airport were also due to resume today after all services were cancelled yesterday from the region.

Given the backlog, passengers were advised to check their flight status online before heading to the airport.

Passengers scheduled to fly out today had to get in line behind passengers who had been waiting since Friday evening.

Volcano unleashes three ash plumes

Federal Infrastructure Minister Warren Truss said in a statement the VAAC had been monitoring three ash plumes, the first of which made its way over central Australia.

"Depending on wind and other weather conditions, the ash has the potential to affect flights to and from others airports, including Brisbane, during coming days," Mr Truss said in the statement.

"This is currently being fully assessed."

How does volcanic ash affect aircraft? Volcanic ash is made up of fine pulverised rock and gases which transform into droplets of sulphuric acid and other substances.

Volcanic ash is made up of fine pulverised rock and gases which transform into droplets of sulphuric acid and other substances. If ash melts in the hot section of a plane's engine, it can form a glass-like coating which can cause loss of thrust and possible "flame out" (engine failure).

If ash melts in the hot section of a plane's engine, it can form a glass-like coating which can cause loss of thrust and possible "flame out" (engine failure). Ash can also cause abrasion of engine parts, and the body of the aircraft, as well as possibly clog the fuel and cooling systems.

Ash can also cause abrasion of engine parts, and the body of the aircraft, as well as possibly clog the fuel and cooling systems. Ash can cause costly damage to aircraft, prompting many airlines to undergo expensive re-routing to avoid ash on their regular routes.

Ash can cause costly damage to aircraft, prompting many airlines to undergo expensive re-routing to avoid ash on their regular routes. It is estimated that volcanic ash has cost the aviation industry more than $250 million since 1982. Source: Darwin Volcanic Ash Advisory Centre

The first ash cloud, which was between 20,000 and 40,000 feet (6 to 13 kilometres), had been moving in a south-easterly direction at approximately 120 knots.

The first recorded eruption of Mount Sengeang Api was in 1512, with several eruptions recorded in the 1990s and only weak steam plumes in the last few years.

The island is now largely uninhabited, but it is still used by locals for farming.

It is understood more than 200 families who work on the island's plantations were evacuated, as well as a further 7,300 people from four neighbouring villages.

Indonesia, which is home to around 130 active volcanoes, sits on the "Pacific Ring of Fire", a belt of seismic activity running around the basin of the Pacific ocean.

In February, a huge volcanic eruption on the main island of Java killed several people, forced mass evacuations and prompted the closure of seven airports.