LA PRIMAVERA, Colombia (Reuters) – “This is HK4679 G on a humanitarian flight between La Primavera and Cumaribo, transporting COVID-19 tests at 3,500 feet,” Ernesto Perez radioed to a nearby military base as he piloted his twin-engine plane above Colombia’s wide eastern plains.

Perez, who works in financial technology, requested permission to detour to avoid storm clouds, guiding the disinfected aircraft to one of the Andean country’s remotest towns.

He is among about 100 owners of private aircraft who answered a call from President Ivan Duque to help transport doctors and medical supplies to the farthest-flung areas of Colombia.

Without the planes it would be impossible to get coronavirus tests from rural areas to urban labs before samples are damaged. Duque has called the pilots “silent heroes.”

“It was a call from the president, who needed to connect the most remote areas of the country so we could pick up the samples that will be tested in Bogota,” Perez said on the runway in La Primavera before heading to his next stop. “In the rainy season it’s impossible by road.”

The private planes have transported thousands of samples and dozens of doctors on more than 200 flights since a state of emergency was declared in March, including taking medical staff to Arauca province, on the border with Venezuela.

Waiting for the plane in La Primavera, in Vichada province, were two hospital officials and 34 coronavirus samples.

The town has no confirmed cases of coronavirus, but officials are conducting random testing.

“(The planes) are an excellent service because of the difficult access,” said hospital bacteriologist Diana Carolina Galvan.

The plane also collected 47 samples from the town of Cumaribo.

Colombia has more than 39,000 confirmed cases of coronavirus and nearly 1,300 deaths.

Perez said he worries about getting infected but will keep flying because he wants to help.

“It’s an absolute satisfaction.”