The Federal Aviation Administration lifted its nationwide ground stop Friday evening after a communications failure disrupted air traffic control centers across the country, grounding departing flights for more than four hours.

Travelers should still expect delays and cancellations as airlines work to get flights and crews back on schedule, the FAA said.

Matt Wilkenson, who was traveling to San Antonio from Washington, D.C., said he learned about the ground stop after receiving a text from a coworker.