Southwest Airlines was forced to temporarily ground all fights on Tuesday (April 18) due to technical problems.
"Early this morning, a vendor-supplied firewall went down, and connection to some operational data was unexpectedly lost," Southwest said in a statement. "Southwest Teams worked quickly to minimize flight disruptions."
While the ground stop lasted less than an hour, it caused over 1,800 delays, according to FlightAware. That accounts for 43% of Southwest's flights.
Only nine flights were canceled, and it is unknown if those cancellations are related to the issue.
The technical issue comes a few months after the airlines suffered a massive meltdown during the Holiday season. Problems with the company's flight scheduling software and bad weather resulted in thousands of canceled flights and cost the airline over $800 million.
The airline has since upgraded its software, and the latest issue is not related to the scheduling software.