The Defence Department has confirmed the index case who triggered a three-day lockdown in Greater Darwin and Katherine is an employee of one of its contractors.
The man in his 30s flew from the United States to Sydney, where he spent two weeks in hotel quarantine, before flying to Darwin via Canberra airport last Thursday.
After spending several days in Darwin, the man travelled by car to a hotel and supermarket in Katherine on Sunday, where the NT Chief Minister said he was "required for his work".
In a statement, Defence told the ABC the man's employment relates to its operations.
However, it would not confirm any further details about the man's role, citing privacy reasons.
The Tindal RAAF base, which is undergoing a $1.1 billion expansion, is just 15 kilometres from Katherine.
On Monday, when the positive case was first revealed, NT Chief Health Officer Hugh Heggie spoke generally about the need for essential workers, including aircraft technicians, to continue to come to the Territory throughout the pandemic.
"We may not have the expertise in this country to actually look at the safety, maintenance or repair of something like that."
Chief Minister Michael Gunner said the man had been "extremely cooperative" in helping contact tracers track his movements.
But he said the man had refused to disclose a key bit of information.
"He won't divulge his vaccination status," Mr Gunner said.
"So we have to operate as if he is unvaccinated."
The man was transferred to the quarantine facility at Howard Springs following his positive test result.
While in Katherine, he went shopping at Woolworths and checked into the Knotts Crossing resort.
Thirteen people at the resort and one at the Katherine Woolworths are considered close contacts, while almost 250 at the Katherine Woolworths are casual contacts.
Many more people have been deemed close or casual contacts in Darwin.
Defence said none of its facilities had been identified as exposure sites.
"Defence continues to work closely with all state and territory authorities who are managing the public health response," it said.
