As many as 24 flights of Indian airlines received bomb threats on Sunday, according to sources.
IndiGo, Vistara, Akasa Air and Air India and Akasa Air are among the airlines that received bomb threats, including international flights, they added.
Six flights each of IndiGo, Vistara and Air India received the threats.
So far this week, more than 90 flights have received bomb threats and most of them have turned out to be hoaxes.
In separate statements, an IndiGo spokesperson said the airline is cognisant of a situation involving flight 6E 58 (Jeddah to Mumbai), 6E87 (Kozhikode to Dammam), 6E11 (Delhi to Istanbul), 6E17 (Mumbai to Istanbul), 6E133 (Pune to Jodhpur) and 6E112 operating (Goa to Ahmedabad).
Vistara said it got security threats for six flights -- UK25 (Delhi to Frankfurt), UK106 (Singapore to Mumbai), UK146 (Bali to Delhi), UK116 (Singapore to Delhi), UK110 (Singapore to Pune) and UK107 (Mumbai to Singapore).
"In line with the protocols, all relevant authorities were immediately notified, and security procedures, as directed by them, are being carried out," a Vistara spokesperson said in a statement.
Security alerts were received for six Akasa Air flights -- QP 1102 (Ahmedabad to Mumbai), QP 1378 (Delhi to Goa), QP 1385 (Mumbai to Bagdogra), QP 1406 (Delhi to Hyderabad), QP 1519 (Kochi to Mumbai) and QP 1526 (Lucknow to Mumbai).
"Following defined procedures and thorough inspections of six aircraft, they have been released for operations," an Akasa Air spokesperson said in a statement.
The sources also said there were threats for at least six flights of Air India flights. There was no comment from the airline.
Against the backdrop of bomb threats, mostly through social media, to airlines, the Bureau of Civil Aviation Security (BCAS) held a meeting with representatives of airlines on Saturday.
The civil aviation ministry plans to put in place strict norms to prevent incidents of hoax bomb threats to airlines, including placing the perpetrators in the no-fly list.
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