Plans to increase the Howard Springs COVID-19 quarantine facility's maximum capacity are lagging, along with Northern Territory Health's staff recruitment drive for the centre.
Prime Minister Scott Morrison said in early March that The National Centre for Resilience would expand to accept 2,000 returned Australians a fortnight, up from 850.
Work to upgrade the facility and recruit extra workers started in April with hopes the centre would reach its new maximum capacity by late May or June.
But on Friday, the NT government confirmed just 1098 people were quarantining at Howard Springs and staff numbers had not reached the planned 400 workers required to enable this.
"We have received over 3,000 registrations of interest for health and operational staff ... and are continuing to work through these to recruit additional staff as we scale up our capabilities," an NT government statement said.
About 80 per cent or 320 of the required 400 staff have been recruited, the statement said.
But not all are ready to work, with over 30 expected to start training sessions next week.
Tens of thousands of Australians remain trapped overseas amid the ongoing coronavirus crisis, with many registered for federal government assistance to fly home.
Howard Springs was supposed to help increase the numbers that could return but just 627 of the people currently quarantining there have been repatriated from overseas.
The remaining 468 are domestic travellers, many of them arriving in the NT from Victoria, which remains in lockdown as a virus outbreak climbs to 65.
Many of the repatriated Australians quarantining at the facility have travelled from India, where about 9000 Australians are registered as wanting to return, including 900 people considered vulnerable.
Flights from the COVID-19-ravaged nation resumed on May 15 following a pause when infection rates soared among returnees at Howard Springs.
The delay in the expansion of Howard Springs comes amid ongoing debate about the effectiveness of hotel quarantine.
It's been found to be the source of numerous recent outbreaks across Australia, including the current one in Victoria.