An airport in Saint Petersburg in Russia suspended all flights on Tuesday due to an unidentified object in the sky.
The government of Russia's second city announced the closure of Pulkovo Airport on its official Telegram channel, without providing a reason for the suspension.
An Aeroflot flight SU1001 made a U-turn and was returning to Kaliningrad, probably because of the restrictions in Saint Petersburg airspace, FlightRadar24 said earlier.
Flights had resumed by noon, with Russian news agencies reporting that the temporary airspace ban within a 200km radius of the airport had been lifted.
A source in the city's emergency services said earlier that an unidentified object, possibly a drone, had been spotted, prompting the initial closure.
Unconfirmed media reports from two online Russian news outlets reported that fighter jets had been despatched to investigate. They later said that the jets had not found anything.
There was no official comment on what caused the disruption or on how the alleged unknown object was investigated.
Data from the FlightRadar24 website showed a number of flights headed for Saint Petersburg turning back to their destinations early on Tuesday, while the airspace closure also appeared to affect flights en route to the Russian exclave of Kaliningrad, which requires planes to fly over Saint Petersburg.
By 12pm local time flights had resumed flying towards the city, the FlightRadar24 website showed.
In a briefing after flights had restarted, Kremlin spokesman Dmitry Peskov said President Vladimir Putin had been kept fully informed of the situation. He declined to comment on the cause of the hour-long disruption.
