The Jet Airways flight had landed in Kolkata and was being cleaned before a scheduled flight to Patna when the cleaners found two bags with the gold stashed inside, Customs official Mona Priyadarshini said.
Priyadarshini said the gold bars weighed around 1 kilogram each. Customs officials confiscated the stash and are investigating.
According to the Hindustan Times, customs officials said the bars bore the stamp of United Arab Emirates and were probably on the way to Mumbai.
India is one of the world's biggest consumers of gold. The government increased the gold import duty recently, which officials say has encouraged smuggling.