At least 10 Indian flights have been subject to bomb threats in the past 48 hours, leading to long delays and diversions.
On Tuesday, the Singapore Air Force sent two fighter jets to escort an Air India Express plane away from populated areas following a bomb threat.
A few hours earlier, an Air India plane flying from Delhi to Chicago had to land at a Canadian airport as a precaution.
False bomb threats against airlines are not unusual in India, but it is unclear what triggered the sudden increase since Monday.
Officials at the government's Directorate General of Civil Aviation and Civil Aviation Safety Bureau did not respond to BBC emails for comment.
Apart from Air India, IndiGo, SpiceJet and Akasa Air flights have also received threats.
On Monday, three international flights taking off from Mumbai were diverted or delayed after user X (formerly Twitter) posted threats. Police arrested a teenager in connection with the case.
On Tuesday, seven flights, including the two Air India planes, were affected by threats made by another now suspended X handle. Screenshots of some messages show that the user tagged the airline and local police and mentioned the flight number.
Air India said in a statement that it was cooperating with authorities to identify those behind the threats and would consider legal action to recover damages suffered.
Every airport in India has a Bomb Threat Assessment Committee which assesses the severity of the threat and takes action accordingly. A threat can result in the intervention of bomb squads, sniffer dogs, ambulances, police and doctors.
Passengers are unloaded from the plane along with their carry-on bags, check-in bags and cargo, and they are all screened again. Engineering and security teams are also searching the plane before it is allowed to fly again.
The resulting delay can cost airlines and security agencies thousands of dollars in damages.
For flights to other countries, this may also lead to the intervention of international agencies, such as in Singapore and Canada.
On Tuesday, Singapore's defense minister said two of the city-state's fighter jets “took off and escorted” the Air India Express plane before it landed safely at the airport from Changi. The plane was flying from Madurai in India to Singapore.
“Once on the ground, the plane was handed over to airport police. Investigations are ongoing,” Ng Eng Hen wrote.
The plane then landed safely at China's Changi Airport.
In Canada – where the Chicago-bound Air India flight landed at Iqaluit airport as a precaution – the Royal Canadian Mounted Police said it was investigating the threat.
Air India said Wednesday that a Canadian Air Force plane was taking the passengers to Chicago. It is not yet clear when the Air India plane will be allowed to take off.
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