The news comes after Mumbai airport was put on high alert after warning from Intelligence Bureau (IB. (Read more: Terror from skies? Mumbai Airport on high alert).
The security around Chhatrapati Shivaji International Airport has been tightened after there were reports of possible threat from an aircraft. The measures have been taken keeping in mind the third anniversary of Sept 13, 2008 Delhi bombings.
Reports also suggest that terrorists may use small aircraft for the attacks in lines with the Sep 9/11 attacks in America. Many sites are already under surveillance and the Delhi's Intelligence Bureau is specially being guarded after the reports.
The warning also comes a week after the Sept 7 bomb blast outside gate number 5, Delhi High Court which left 13 dead and more than 70 injured.
Delhi has also been put on high alert and at least 20,000 personnel have been deployed across the city to carry out extensive search following the third anniversary of 2008 Delhi bombings. Security across malls, market places and other crowded areas have also been intensified.