it could also depend on what card you're using (issuing bank). Capital One (Visa) did not work with IndiGo. was first rejected, then accepted after I called Capital One and told them to authorize it (had to tell them how much I was charging).
SpiceJet: Worked fine (a couple months ago, before the new regulation)
airindia.com/indianairlines.in: Works, as long as their site is running
+1 with Travelocity India - HSBC Mastercard worked fine, first time.