Restrictions that temporarily barred U.S. airlines from operating in parts of the Caribbean and South American airspace were lifted early Sunday, allowing flights to resume after a day of widespread disruptions.

The limits followed multiple Notices to Airmen issued Friday by the Federal Aviation Administration, citing safety risks linked to military activity in Venezuela across the Curacao, Maiquetia, Piarco and San Juan flight information regions.

U.S. Transportation Secretary Sean Duffy said late Saturday that the restrictions expired at midnight Eastern Time and that airlines were clearing backlogs. He advised travelers to check directly with carriers as schedules were updated.

United Airlines said it was preparing to resume Caribbean flights, beginning with service to San Juan, Puerto Rico, after hundreds of cancellations at Luis Muñoz Marín International Airport on Saturday. The airline expects to operate most scheduled flights Sunday and plans additional services to assist affected passengers.

JetBlue also began restoring service and said it may add extra flights. The carrier said about 215 flights were canceled during the disruption and urged customers to monitor flight status online or through its mobile app.

In Europe, a conflict-zone advisory for Venezuelan airspace issued by the European Union Aviation Safety Agency remained in effect, but Dutch carrier KLM said it would operate scheduled flights Sunday after canceling services to several Caribbean destinations a day earlier.

Local and regional airlines were largely unaffected, as the FAA restrictions applied only to U.S.-registered carriers, allowing most intra-regional travel to continue with limited disruption.