The Civil Aviation Security Bureau has written to the police chiefs in each state, the CISF or paramilitary force which guards airports, as well as to state-run and private airlines alerting them to the security threat.
Jammu and Kashmir, Punjab, Rajasthan and Gujarat -- all border states -- have, like Delhi, been marked for careful vigil.
22 airports in the four cities have been sent detailed warnings and authorities have confirmed high security measures are being implemented.
While baggage will be subjected to more random and detailed checks, parking lots as well as loading areas used by airport vehicles will be more carefully monitored.
A high security alert is standard for the festival season. But agencies are concerned about a terror attack in retaliation for last week's surgical strikes in Pakistan-Occupied Kashmir which saw soldiers targeting seven terrorist launch pads or gathering areas.
Yesterday, National Security Advisor Ajit Doval briefed Prime Minister Narendra Modi on security at the Line of Control in Jammu and Kashmir. Intelligence agencies have warned of nearly 100 terrorists being prepped to cross the de-facto border before winter sets in and the routes into Kashmir are covered with snow.
