The majority of flights in and out of Darwin have been cancelled today because of a volcanic eruption in Indonesia.

A spokesperson for Darwin Airport says all international and domestic Jetstar services, and all domestic Virgin and Qantas flights have been cancelled.

The Sangeang Api volcano, which is located off the north east coast of Sumbawa island, erupted yesterday evening.

The Bureau of Meteorology says it has caused a volcanic ash cloud that is moving in a south-easterly direction, affecting the Kimberley and Top End.

A spokesperson for the Darwin Volcanic Ash Advisory Centre says the ash is moving further south and dispersing.

"As it begins to move away from the volcano, it begins to dissipate so we see less and less of a signatory in the satellite imagery," the spokesperson said.

"We expect over the next 24 hours it should gradually fade out so it's no longer a significant threat to the area.

"It's been almost a continuous eruption since about, I think it would've been about 6:30pm last night local time in Indonesia.

"There's been three high level eruptions during that period. However, right now we can still see a significant eruption going on at the volcano."

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Virginia Sanders from Darwin International Airport says it is not yet known when flights will resume.

"At this stage it's speculation ... from what I can tell, as the ash moves it dissipates so it could be good news for tomorrow."

"But going on past experience, this is usually [a] 24-hour type event."

In a statement on their website, Qantas says they are closely monitoring weather conditions and will release updates as they become available.

"Due to the overnight eruption of a volcano on the southern Indonesian island of Sangeang, volcanic ash plume has drifted over the Australian Northern Territory coastline," the statement said.

"As a result, all Qantas flights to and from Darwin have been cancelled for Saturday 31 May 2014."

Virgin Australia also released a travel alert, saying they will recommence normal operations as soon as the volcanic ash safely allows it.

"Our team of meteorologists are continuing to monitor the situation, in consultation with the Volcanic Ash Advisory Centre in Darwin," the alert said.

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

Passenger hopeful Jetstar flight will leave tonight

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

Hundreds of passengers are sitting around Darwin airport, and some are confused as to whether their flights have been cancelled.

Jetstar passenger Paul Gallagher was scheduled to fly home to Sydney tonight.

He says a Jetstar spokeswoman told him his flight has not been cancelled.

"She said that the flight's still confirmed but she says ... they're still collecting information and they would ring me if they heard anything more."

The Bureau of Meteorology is expected to provide airlines with an update on the size of the ash cloud later this afternoon.

Jarrod Bowditch says he is trying to get to Broome for a friend's wedding.

"The wedding isn't until next weekend but the bucks starts tomorrow, so hopefully we get there in time," he said.

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 have been evacuated following yesterday's eruption.