FedEx Express, the delivery giant’s rush service, told Fortune that it is now handling the delivery of swabs taken at federal community-based sites, as well as at a handful of drive-up sites at national store chains, to testing labs.

The initiative to use big retailers’ large stores was announced three weeks ago, on March 13, by President Trump and the chief executives of Walmart and Target and senior executives of Walgreens and CVS pharmacy, along with C-suite executives at the health care companies carrying out the tests, Quest Diagnostics and LabCorp.

The goal was to make testing widely available by offering them in the parking lots of the country’s largest store chains. Those retailers operate nearly 30,000 stores in all parts of the country. The ramp-up has been slow as the companies figure out logistics and wait for tests to become more widely available.

But the volume is starting to rise, says FedEx Express. The Department of Health and Human Services (HHS) told Fortune on Friday that there are currently 41 federal community-based testing sites.

FedEx Express CEO Donald Colleran said that because the Federal Emergency Management Agency (FEMA) and HHS need swabs to be delivered overnight to labs, even if taken on the weekend, the company has added 28 flight legs by tapping its network of planes and trucks. It does not typically offer overnight service on weekends.

The $14-billion-a-year FedEx unit had to quickly spring into action to create that extra infrastructure to pick up tests and deliver them: Colleran said the White House approached the company on March 13, the day of the press conference.

“We have a really unique seat to what’s going on,” said Colleran, who took the reins of FedEx Express last year after more than three decades at the company.

The initial test case was at a CVS pharmacy store’s parking lot last week in Shrewsbury, Mass., just outside Boston—the first drive-up location. Others have followed, including two Walmart parking lots near Chicago and at a Rite-Aid in Philadelphia. At first, the tests were available only for emergency workers and not the general public. But at some locations, including the Shrewsbury CVS, that is being expanded to people 65 and older with symptoms. Last weekend alone, FedEx Express delivered 20,000 tests to labs.

Because of the nature of the item being shipped, FedEx uses extra precautions, Colleran said. FedEx creates a “geo-fence around each package, which will include several specimens” so it can be tracked in real time on its way to the destination lab. The packages have features to monitor temperature and light variances to protect the tests.

“We’re the quarterback in all this in terms of logistics,” Colleran said.

Across the country, there is a race to get faster-result coronavirus tests widely available for the broader public. Most people cannot get a test if they have no symptoms, but if someone gets the green light for a test, it typically takes days to get the test done. As of April 1, only 1.3 million tests had been given in the United States.

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