Who placed this crude bomb, how, and in which city?

The Special Investigation Team (SIT) thinks it's possibly Thiruvananthapuram, since the bomb was wrapped in a Malayalam newspaper and a Kerala Board answer sheet. (Read: Security lapse: Explosive found on aircraft)

That apart, the probe on the Kingfisher Bomb Scare has hit a dead end.

The Kerala police made a late-night whistle-stop tour to Bangalore: They questioned the airlines staff, scanned the CCTV footage but returned with little. Now the Bangalore police will do the same at Thiruvananthapuram.

While the SIT questioned the ground-handling staff and other officials at the airport, the local police here screened the passengers who were on that aircraft.

The Valiyathura Police Station which has registered a case under section 4 and 5 of the Explosives Act has summoned 22 passengers, of which they have taken the statements of 15 passengers.

Security has been tightened in airports across the country.

The Bureau of Civil Aviation Security has asked airlines not to accept couriers without properly verifying the sender.

Meanwhile, the pressure from the Special Investigation Team is increasing as many top cops feel this was part of a security test of airports by terrorists.