The Department of Defence is working with health authorities to track down the source of a COVID-19 case on the Williamtown RAAF base.
It is believed a person working in the No. 2 Operational Conversion Unit, which teaches fighter pilot skills, tested positive last week.
About 3700 military and civilian personnel and up to 500 contractors work at the base in a variety of capacities.
Operations at the adjoining Newcastle Newcastle Airport have been unaffected by the outbreak, however, some surrounding businesses have shut down.
A Department of Defence confirmed the outbreak on Sunday night.
"A comprehensive public health response is now underway under the direction of NSW Health," a spokeswoman said.
"RAAF Base Williamtown was already subject to the Hunter Region stay at home orders and all appropriate measures are being taken in accordance with NSW Health requirements"
BAE Systems Williamtown, which interacts with the base for the maintenance of aircraft, took the precautionary step of closing to allow contact tracing to proceed as effectively as possible.
"We continue to update our guidance to employees to reflect the latest Australian Department of Health advice and ensure we're taking appropriate precautions to protect our people," BAE Systems Director Aircraft Sustainment and Training Andrew Chapman said.
"We have robust business continuity plans in place which are under constant review as the situation evolves and we continue to work closely with employees, customers and suppliers to minimise any impact to our operations.
"We're closely monitoring the impacts of COVID-19 on the operations of our business and we are continuing to work closely with our customer and stakeholders.
We're thankful for the continued support and co-operation of our employees during this period of unprecedented challenge and uncertainty, as we all play our part in tackling this public health emergency.
