The alert has been sent after it was found that several crores of rupees in demonetised banknotes were transported in a chartered jet from an airstrip in Hisar to Dimapur airport in Nagaland.
"All airports have been alerted and directed to keep strict vigil on illegal transportation of cash," an official said.
Central Industrial Security Force (CISF), which protects nearly all 98 airports in the country, and Central Reserve Police Force (CRPF) have been given clear instructions to be on high alert against any such attempt to convert black money into the banking system.
During the searches at a few premises owned by a Dimapur businessman, the taxmen were able to locate the missing Rs 3.5 crore. Not only that, they impounded another Rs 4.47 crore in demonetised Rs 500 and Rs 1000 bills.