Flights to US on high alert against hijacks New Delhi, Nov. 12: Americas Federal Bureau of Investigation has sent a communication to Indias Intelligence Bureau warning against an imminent terrorist threat, probably in the form of a hijack on US-bound flights from Indian airports. The FBI received an email that is believed to have originated from India, warning of terror attacks. Following the alert that was conveyed on Saturday, the IB informed the Bureau of Civil Aviation Security (BCAS), which promptly despatched a communication to the Central Industrial Security Force (CISF), which is responsible for guarding airports in India. Airports across the country and airlines operating flights to the United States have also been alerted. Security has been beefed up further. This increased security is particularly visible at the international airports in New Delhi, Mumbai, Kolkata, Chennai and Bangalore. The BCAS has advised that security be increased by way of strict baggage checks, physical checks and profiling of passengers on all US-bound flights for the next one week. All passengers on US-bound flights have been advised to come to the airport earlier than would have been required otherwise, as the stringent additional checks would require time. The latest terror alert follows the one on November 9 when an anonymous letter was found at Trichy airport in Tamil Nadu, warning that Al Qaeda would blast Chennai airport like the airports in Thailand. The note also warned of attacks on Trichy, Madurai and Coimbatore airports, as well as airports in Kerala. Civil aviation secretary Ajay Prasad had also recently listed a series of measures, which include a high level of security at airports, access control, perimeter guarding, increased surveillance, physical searching of hand baggage and 100 per cent checking of baggage. But what is more worrying is that the aviation sector has been hit by a series of terror alerts in the second half of this year, which started with the London terror alert three months ago in which terrorists were believed to have been conspiring to cause explosions on board aircraft using inflammable liquids. After that, the Indian government initially barred passengers from carrying any liquids at all in their hand baggage, but later relaxed the ban to allow some liquids to be taken on board. Our Chennai special correspondent adds: Chennai airport director Dinesh Kumar told this newspaper that security there was already high following the Trichy alert, but was now being intensified further. All passengers and their baggage were being screened thrice before being allowed on board. Visitors entry had being restricted and cars were not allowed to be kept for more that three hours in the airport parking lot except if a driver was sitting inside. The departure of the Lufthansa flight to Frankfurt, Air France to Paris and British Airways to London from Chennai got delayed in the early hours of Sunday due to the last-minute extra checking. A top Tamil Nadu intelligence officer said a number of security loopholes needed to be plugged. For instance, he said, the passenger is allowed to keep his baggage after it was screened until it was loaded on to the plane, and it is possible to slip something into the baggage in (this period). We must avoid this. He added: We will soon have cameras to record faces of passengers as they enter the airport, even cars as they come into the complex and drive out. We will be able to track any car that has been inside the airport complex for over three hours. It would be a good idea, he said, if passports were to contain fingerprints, so that the use of fake travel documents could be eliminated. A TV report had said that an Internet centre in the US had received an email warning that a plane flying from India to a destination in Europe or the United States could be hijacked. This email was then passed on to the FBI, which in turn informed the Indian authorities, the TV report added.