Peabody CEO Glenn Kellow told an analysts' conference that most of the cost improvements had occurred at the company's open cut mines. 

"The mines have demonstrated cost per ton improvements when comparing second quarter actual results to the financial year 2019 performance," he said.

"And that's even with substantially lower volumes.

"These improvements are most notable across our surface operations. They quickly responded to and overcame rapidly declining demand."

Kellow said cost per ton in Peabody's surface operations improved 6% compared to the prior year even as volumes dropped nearly 30%.

"Our underground room and pillar operations have also responded well to challenging conditions," he said.

"Our longwall operations, however, have not been able to respond as quickly to lower demand.

"As you could imagine, [winding] down production in the longwall operation is a bit more difficult given complexities with fixed costs and often the geotechnical desire to advance the wall."