The discounts are valid for travel between March 1 and March 31 on mostly eastern routes such as Kolkata-Aizawl (Mizoram),Guwahati (Assam), Agartala (Tripura), Bagdogra (West Bengal), Silchar (Assam) apart from Mumbai, Delhi, Chennai and Vishakhapatnam.
Last week, it offered 7% discount on its flights from India to Dubai, the latest in a slew of offers in the ongoing lean travel season.
Airlines offer discounted rates during the months of February to April as fewer holidays and festivals lead to a dip in air travel.
SpiceJet's offer is valid for booking between March 1 to 15, for travel until the end of this month.
Last month the airline announced a flat 10% discount on flights to Muscat from India.