Federal officials halted Southwest Airlines flights from taking off on Tuesday morning. 

By late morning on the East Coast, more than 1,500 Southwest flights had been delayed, accounting for well over half of all delays nationwide, according to FlightAware.

The Federal Aviation Administration just after 11 a.m. Eastern reported that the pause had been lifted and normal operations have resumed.

It appears that Southwest flights were ground-stopped across the country. 

Just after 11 a.m. Eastern, Southwest issued a statement saying it has resumed normal operations and that data connection issues due to a firewall failure were to blame for widespread delays. 

"Southwest has resumed operations after temporarily pausing flight activity this morning to work through data connection issues resulting from a firewall failure. Early this morning, a vendor-supplied firewall went down and connection to some operational data was unexpectedly lost. Southwest Teams worked quickly to minimize flight disruptions.

"We ask that travelers use Southwest.com to check flight status or visit a Southwest Airlines Customer Service Agent at the airport for assistance with travel needs. We appreciate the patience of our Customers and Employees during this morning’s brief disruption."

This is a developing story. Stay with Spectrum News for updates.