A commercial aircraft contracted by the ADF and carrying Australian defence personnel has been forced to make an emergency landing after smoke and fumes filled the cabin.

At least three people were taken to hospital suffering smoke inhalation soon after the plane returned to Darwin International Airport yesterday.

Private Australian company Strategic Aviation had been hired by the Australian Defence Force to transport passengers and light cargo as part of a "regular sustainment service" to Kuwait, a defence spokeswoman said.

She was unable to confirm media reports that there had been 80 ADF personnel aboard the flight.

Simon Moore, commercial manager of Strategic Aviation, said the plane was 40 minutes into the eight-hour flight when the crew noticed "a strong smell within the cabin".

"The captain and crew followed normal operating procedures and returned to Darwin to investigate the issue," he said in a statement.

"No passengers were affected however three crew members were taken to Darwin hospital as a precautionary measure."

But a Darwin Airport spokeswoman said those taken to Royal Darwin Hospital, and later released, were "one crew and two passengers".

The airport spokeswoman described the incident as a "full emergency situation with smoke and fumes in cabin".

The plane was currently parked at the airport with "all doors and hatches open," she said.

Mr Moore said the "irregular smell" was believed to have come from an air-conditioning system.

It is currently being in investigated by the company, with the ADF saying in a statement it believed "a technical fault" had forced the landing.

"The aircraft landed safely and without further incident. All company and operational procedures were followed," Mr Moore said.

The defence spokeswoman said no ADF personnel were injured as a result of the incident and the department would not release details about how many people were on board the flight.

"Personal details of the ADF personnel aboard the flight will not be released," she said.