Air traffic controllers across the country have grappled with radar and communications outages for years, CNN review finds.

MAY 19: NEWARK On Monday, a two-second air traffic control radio frequency outage-–the fourth communications breakdown in a month-–occurred at Newark Liberty International Airport, Reuters and CNN reported.

According to the New York Post, a blackout on April 28 for air traffic controllers overseeing Newark led to many workers taking trauma leave, exacerbating its staff shortage. In addition, a Newark Airport runway is closed for “rehabilitation work” leaving the airport with only one functioning runway.