The decades-long shortage of air traffic controllers in the U.S. won’t be solved anytime soon, even with a hiring blitz.

Several air traffic control facilities, including in Nevada, are understaffed, a decades-old trend that could be getting worse after the Trump administration laid off hundreds of Federal Aviation Administration employees earlier this month. The FAA is the federal agency that regulates civil and commercial space transportation.

U.S. Transportation Secretary Sean Duffy said on Thursday the Trump administration will take steps to boost air traffic controller hiring after a series of recent safety incidents again raised questions about a persistent staffing shortage.