Jet, India's biggest full-service carrier, said in a regulatory filing it had entered an agreement to buy the aircraft, but it did not say whether the agreement was a formal order or a non-binding memorandum of understanding.

This is the third agreement Jet Airways has entered into for Boeing's 737 MAX narrowbody jets over the last one year, taking the total to 225 aircraft. The Indian airline signed firm orders for 75 planes each in October and April.

Based on Boeing's list prices, the latest deal could be worth as much as $9.7 billion depending on which 737 MAX the airline chooses. Airlines usually get significant discounts from manufacturers though, bringing costs well below list prices.

The 737 MAX can seat between 130 and 230 passengers, depending on the variant.

The latest agreement comes as Indian airlines rush to expand fleets to meet ever-increasing demand for domestic as well as international flights, making it one of the most targeted sales markets for Boeing and European rival Airbus SE.

Boeing said in July last year it expected Indian airlines to order up to 2,100 aircraft worth $290 billion over the next 20 years, calling it the highest-ever forecast for Asia's third-largest economy.

Domestic passenger traffic in India has grown at more than 20 percent annually in the last few years despite a lack of infrastructure and air traffic congestion at some of its busiest airports such as Delhi and Mumbai.

(Additional reporting by Aby Jose Koilparambil in Bengaluru; Editing by Raju Gopalakrishnan and Louise Heavens)

By Aditi Shah