The Federal Aviation Administration said Friday night that it has ended its hours-long nationwide ground stop, which has impacted thousands of flights during a busy travel month.

Transportation Secretary Sean Duffy told reporters in a late-night press briefing that they have partially reopened American airspace but warned that flights will only slowly resume. 

The secretary said the outages were caused by an overload of the "incredibly old" air traffic controller system, which relies on an analog system. Duffy urged Congress to approve emergency funding for upgrades.

"This is an emergency," the secretary declared.

Homeland Security Secretary Markwayne Mullin, who was also at the press briefing, said there was no indication that the incident was caused by a cyberattack and downplayed conspiracy theories about the cause.

Mullin said the introduction of some new technology into the air traffic control system is what overwhelmed it and claimed the system needs a complete overhaul, which he estimated would cost $50 billion.

The groundings impacted at least 8,781 flights within, out of or into the United States as of 9 p.m. Eastern, according to FlightAware, and over 6,000 flights have been canceled across the country.

Misty Severi is a news reporter for Just The News. You can follow her on X for more coverage.