Perspectives from ISB

A recent article features IndiGo, which along with SpiceJet, was one of the only two Indian airlines that were profitable in 2011. The parallels with Southwest in the U.S are striking: on-time performance, no-frills service, high aircraft utilization and having only one type of aircraft in its fleet. It makes me wonder if the low fares/no-frills service model is the only sustainable one for the airlines?