Moscow’s four primary airports faced significant challenges in returning to normal operations on Thursday, following Ukraine’s largest drone strike to date that caused extensive travel disruptions, as stated by Russian transportation officials.

According to the Russian Association of Tour Operators, over 60,000 travelers were affected by around 350 delays and cancellations at airports nationwide. Russia’s military reported intercepting 524 Ukrainian drones, which compelled civil aviation authorities to temporarily suspend flights.

“The planes that were not able to reach their destinations on schedule will delay subsequent flights as well,” the Association of Tour Operators explained. “This initial delay will have a cascading effect on future flights.”

Several passengers indicated they experienced delays exceeding 30 hours. Overall, about 12% of all flights to and from Moscow were canceled on Wednesday.

By Thursday morning, Russia’s Transportation Ministry announced that more than 14,000 passengers were still stuck on nearly 100 incoming and outgoing flights at Moscow’s airports, with expectations to resume normal operations by 6:00 p.m. local time.

Nevertheless, the Russian Association of Tour Operators noted that approximately 150 more flights in and out of Moscow faced cancellation on Thursday.

Turkish Airlines and Pegasus Airlines announced the cancellation of around 40 flights connecting Russia with four Turkish cities on Thursday and Friday, impacting over 15,000 travelers.

The ongoing disruptions coincided with President Vladimir Putin hosting numerous world leaders for the May 9 Victory Day celebrations. Serbian President Aleksandar Vučić was reportedly among those affected, making a stop in Azerbaijan before arriving in Moscow late Wednesday.