When international travel resumed in November last year, the airline temporarily re-routed its Perth to London service through the Territory capital.
The Perth service was scheduled to return in April, but with the WA government yet to confirm a reopening date for the state, Qantas says it will continue to operate out of Darwin until at least June this year.
The Sydney to London service will also transit through Darwin instead of Singapore.
Qantas chief executive Alan Joyce said the extension to the Darwin service provided the Territory with an opportunity to capitalise on pent-up international inbound travel demand.
"This extension through to at least mid-June means the Top End has several months to properly leverage the opening up of Australia's borders to all tourists," Mr Joyce said in a statement on Tuesday.
"It's a great opportunity to encourage thousands of visitors to stop off in Darwin to see what the NT has to offer."
NT Chief Minister Michael Gunner said the government had also secured a deal with Qantas to establish a new base in Darwin for its 94-seat Embraer 190 aircraft.
Mr Gunner said up to 200 jobs were expected to be created under the 30-month agreement, including pilots, cabin crew and aircraft maintenance positions.
The Territory government will invest up to $3.6 million in training, marketing and promotion, as well as incentives to attract workers to be based in the area.
Qantas has announced plans to launch E190 routes from Darwin to Adelaide, Canberra, Cairns and Townsville by the end of March.
"We are working in partnership with Qantas to deliver more jobs, cheaper fares and more flight routes for Territorians," Mr Gunner said.
