Silence. That’s the last thing an airline pilot wants to hear from air traffic control as they approach a major international airport straddling the country’s most populated city.

Flight delays and cancellations persisted at Newark Liberty International Airport Monday, and the Federal Aviation Administration says some air traffic controllers were taking time off to destress from recent equipment and telecommunications outages.

The root cause is an air traffic controller shortage, a nationwide issue the Trump administration has pledged to fix.