The pattern of domestic airlines receiving bomb threats to their flights continued for the fourth day as two international flights, one each of Vistara and IndiGo, were targeted in the similar manner on Thursday.
Earlier on Wednesday, seven flights of IndiGo, SpiceJet and Akasa received similar bomb threats.
Prior to that, nearly a dozen flights operated by Indian carriers received similar threats on Monday and Tuesday.
On Thursday, a Mumbai-bound Vistara flight with 147 persons on board was immediately taken to security checks on its arrival from Frankfurt following the Boeing 787 aircraft receiving a bomb threat, according to the airline.
At the same time, an IndiGo flight operating from Istanbul in Turkiye for Mumbai also received a bomb threat and was taken to an isolation bay here for the security agencies to carry out a comprehensive security check.
"The Vistara flight UK 028 operating from Frankfurt to Mumbai on October 16, 2024 was subject to a security threat received on social media," the airline said.
As per the protocol, all relevant authorities were immediately informed, it said, adding the aircraft safely landed at the Chhatrapati Shivaji Maharaj International Airport, Mumbai.
"It was taken to the isolation bay where all customers were disembarked. We are fully cooperating with the security agencies to complete the mandatory security checks," Vistara said in the statement.
There were 134 passengers and 13 crew on board the aircraft, a source said.
The aircraft, which departed for Mumbai from Frankfurt on Wednesday at 8.20 pm (local time), made an emergency landing here at around 7.45 am on Thursday, the source said.
IndiGo in a statement said, "Flight 6E 18, operating from Istanbul to Mumbai, received a security-related alert. Upon landing, the aircraft was isolated, and all passengers were safely disembarked."
The airline worked closely with the relevant authorities, and standard operating procedures were followed, it said.
IndiGo, however, did not share other details.
