Eleven flights to and from Calcutta received false security threats through social media on Thursday, which delayed the planned shutdown of the airport, as a precaution against Cyclone Dana, by an hour.

Across the country, more than 90 flights were impacted by security threats on Thursday, a problem Indian airlines have been facing for over a week now. Flights of Air India, IndiGo, Vistara, SpiceJet and Akasa Airlines received bomb threats. At the Calcutta airport, seven flights of IndiGo, two of Alliance Air and one each of Akasa Airlines and SpiceJet received threats, said airport officials.

The IndiGo flights impacted were:

The two Alliance Air flights impacted were:

The SpiceJet flight impacted:

The Akasa Airlines flight impacted:

The impacted flights arriving in Calcutta were taken to the isolation bay and passengers and luggage scanned.

“All customers were safely disembarked. At IndiGo, the safety and security of our customers and crew remains paramount in all facets of our operations.... We sincerely regret any inconvenience this situation may have caused our customers and appreciate their understanding,” IndiGo said in a statement.

“The security procedures led to a delay in suspending flight operations at the Calcutta airport on Thursday evening,” said an official.

Airport officials said this was the fourth time in a week that the Calcutta airport received such bomb threats. They said FIRs have been lodged with police.

In the past few days, more than 170 flights were impacted by hoax threats.