The U.S. Federal Aviation Administration (FAA) has lifted the nationwide ground stop that grounded thousands of flights, but officials say it will take time for operations to return to normal. Southwest Airlines is resuming a limited number of flights tonight, while American Airlines warns of further delays and cancellations.

Some college football games have been rescheduled as teams adjust to travel disruptions. The FAA said it tested its systems before lifting the ground stop and confirmed they were stable and reliable.

Travelers are being advised to check with their airlines for the latest updates on their flights. American Airlines has issued a travel alert to provide customers with flexibility and the option to receive a refund.

United Airlines is also resuming some flights tonight. The FAA says safety remains its top priority and urged travelers to contact their airlines about upcoming flights.