A Qantas plane has been forced to turn around on a flight from Darwin to Alice Springs.

About 115 people were on the Qantas flight number 1935, which left Darwin at 7:30 a.m.

Qantas says about half an hour into the flight there was a fault with the landing gear, which would not retract.

The plane circled Darwin to unload fuel, then landed safely in Darwin at 8:30 a.m.

The aircraft was surrounded by emergency vehicles on the landing strip.

Passengers were unloaded and the plane was towed to another part of the airport.

All of the Northern Territory's Central Australian politicians were on board, including the Central Australia Minister Karl Hampton and four Country Liberals MLAs.

They were returning to Alice Springs after this week's Parliamentary sittings in Darwin.

Country Liberals MLA Adam Giles says they thought at first that the cargo door had come open.

"When we heard the first noise of something that clearly was different from a normal plane flight, I turned to one of my colleagues next to me and said, well, clearly something is wrong here and I think everybody knew that," he said.

But Qantas says the cargo door did not open and the fault was with the landing gear.

"I think there were a few people who had their hearts in their mouths for a minute there," Mr Giles said.

"I mean, these things can go either way at certain times.

"But, fortunately, it went the right way for us and our feet are on solid ground."

A Qantas spokewoman says engineers are now working on the the plane at Darwin airport.

She says when the problem with the aircraft is rectified, the flight will take off again.

She says Qantas will not provide anyone for interview about the incident today.