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

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.

Outages are not just a Newark problem—in recent weeks, at least three other U.S. airports have reported communication breakdowns that left air traffic controllers unable to contact pilots. MAY 19: NEWARKOn Monday,