Nearly 80 domestic and international flights received bomb threats in less than 24 hours that later turned out to be hoaxes, keeping thousands of passengers and security agencies on tenterhooks.

The estimated losses incurred by airlines due to the disruptions would be around Rs 600 crore, according to two former airline officials.

On Tuesday alone, around 50 flights, including 13 each of IndiGo and Air India received bomb threats. Akasa Air got the threats for over 12 flights and as many as 11 flights of Vistara also received the threats, the sources in the know said.

Around 30 flights of IndiGo, Air India and Vistara got bomb threats on Monday night, they added.

In nine days, more than 170 flights operated by Indian carriers have received bomb threats, mostly through social media, that also forced the diversion of some of the international flights.

On average, disruption to a domestic flight would cost around Rs 1.5 crore while the expenses would be around Rs 5-5.5 crore for an international flight, an official, who has worked in the finance department of a domestic airline, told PTI.

A back-of-the-envelope calculation shows that the average cost of disruption caused to domestic and international flights would be around Rs 3.5 crore, and for more than 170 flights, the total expenses or loss for the airlines would be around Rs 600 crore.

The figures are broad based since many other factors like narrow-body and wide-body planes, and duration of a flight also need to be taken into consideration.

Another official, who has served in the finance department of another domestic airline, said the operational costs are higher for wide-body planes compared to narrow-body planes. Apart from direct expenses such as fuel and airport parking charges, there are also indirect costs like impact on overall flight network, due to disruptions, the official added.

In separate statements, an IndiGo spokesperson said 13 of its flights received security-related alerts on Tuesday. These are 6E 196 (Bengaluru to Lucknow), 6E 433 (Aizawl to Kolkata), 6E 455 (Kolkata to Bengaluru), 6E 17 (Mumbai to Istanbul), 6E 394 (Kolkata to Jaipur), 6E 318 (Kolkata to Ahmedabad), 6E 297 (Hyderabad to Jodhpur), 6E 399 (Lucknow to Goa), 6E 381 (Goa to Ahmedabad), 6E 403 (Pune to Dehradun), 6E 419 (Surat to Goa), 6E 323 (Bagdogra to Chennai) and 6E 214 (Mumbai to Srinagar).

Passengers of all the flights disembarked safely at the destination airports.

An Akasa Air spokesperson said some of its flights operating on Tuesday received security alerts and that the airline is following all safety and security procedures in coordination with local authorities.

The airline did not mention the number of flights that received the security alerts.

A Vistara spokesperson said that a few of its flights operating on Tuesday received security threats on social media.

"We immediately alerted the relevant authorities and are following all security procedures as directed by them," the spokesperson said in a statement.

An Air India spokesperson confirmed that some of its flights operating on Tuesday were subject to security threats received on social media.

"Following the laid down protocols, relevant authorities were immediately alerted, and all security procedures strictly adhered to, as per guidance from the regulatory authorities and security agencies," the spokesperson said.

Meanwhile, the protocols for the Bomb Threat Assessment Committee (BTAC), convened in the event of a bomb threat call to an aircraft or airport, have been tweaked to better tackle the spate of the ongoing "random" Internet-based threats being made to various Indian airlines, official sources said on Tuesday.

Also, the government is planning legislative actions to deal with bomb threats to airlines, including placing the perpetrators on the no-fly list.

Amendments are being proposed to The Suppression of Unlawful Acts against Safety of Civil Aviation Act (SUASCA), 1982, whereby the perpetrators could be arrested and a probe can be initiated without a court order for offences when an aircraft is on the ground.

Besides, changes are being planned to aircraft security rules to ensure stringent punishment for perpetrators of bomb threats to flights.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.