IndiGo airline's biggest shareholder will sell a 2% stake worth $394 million in the low-cost Indian carrier on Tuesday, per a term sheet seen by Reuters, marking its first such sale in at least four years during which the company's stock has soared.

Interglobe Enterprises, which had a 37.75% stake in Interglobe Aviation, the operator of IndiGo, will sell the shares at a base price of 4,266 rupees each, the term sheet showed.

That is a 6.6% discount to the stock's closing price on Monday. The stock slid 3.6% to 4,403.40 rupees on Tuesday.

Interglobe Enterprises, led by Rahul Bhatia, the co-founder of IndiGo, cannot sell further shares for another 365 days, the term sheet showed.

This is Interglobe Enterprises' first stake sale in at least four years, per exchange data, during which the stock has more than quadrupled in value.

In contrast, Rakesh Gangwal, IndiGo's other co-founder, and his wife Shobha have trimmed their stake for more than a year now through multiple share sales.

Still, IndiGo's stock has risen roughly 85% over the last one year, hitting multiple all-time highs during that period.

Interglobe Enterprises also operates in the hospitality as well as logistics sectors, and has partnered with U.S.-based Archer Aviation to start electric air taxis in India.

Around 1.1 million IndiGo shares changed hands via block trades on Tuesday, per National Stock Exchange data, all at a discount to the last closing price, but above the base price.

IndiGo has over a thousand jets on order from Airbus, is betting on long-haul travel and will introduce business-class cabin later this year.

Citigroup is the sole broker for the deal. (Reporting by Scott Murdoch and Nandan Mandayam; Editing by Savio D'Souza)