India’s airlines are set for a landmark week, with two milestones days apart, that will redefine the competitive landscape in one of the world’s fastest-growing aviation markets.

Vistara operates its final flight on Monday before its planned merger with Air India kicks in the following day, marking the end of a complex and messy two-year long process. On Thursday, market leader IndiGo, operated by InterGlobe Aviation Ltd., debuts its business-class cabins on select routes as it ventures beyond budget travel for the first time.