The centers were originally expected to take patients with non-COVID-19 conditions to relieve pressure from hospitals.
Less than half of the 2,000 ventilators the DoD promised have been allocated, despite a desperate need across the country.
The service will operate under a "reset" to determine which ops are necessary and which it can forgo until a later date.
The Defense Department is preparing to send them to states overwhelmed by the rising pandemic death toll.
The 531st Hospital Center was headed to New York, which is struggling to deal with number of coronavirus cases.
Sites in New York, California and Seattle are among those on the list.
2,050 citizen soldiers and airmen have been activated by state governors, and that number will likely double by the weekend.
The Defense Production Act of 1950 was signed by President Truman amid concerns about supplies and equipment during that war.
President Trump said Wednesday that the Navy's pair of hospital ships will soon be stationed on the East and West coasts.
The U.S. has seen a shortage of testing kits as the novel coronavirus, or COVID-19, spreads.