At the National Institutes of Health, six directors — from institutes focused on infectious disease, child health, nursing research and the human genome — are leaving or being forced out. At the Federal Aviation Administration, nearly a dozen top leaders, including the chief air traffic officer, are retiring early. And at the Treasury Department, more than 200 experienced managers and highly skilled technical experts who help run the government’s financial systems chose to accept the Trump administration’s resignation offer earlier this year, according to a staffer and documents obtained by The Washington Post. Across the federal government, a push for...