JetBlue and Singapore Airlines have introduced reciprocal mileage-earning. This relationship makes a lot of sense for both airlines, and it makes a lot of sense for passengers. There are good, strategic reasons to select one earning option or the other for your flying.
In fact this relationship makes flying JetBlue a lot more attractive for me, since the biggest drawback in my mind (besides having their “Mint” first class product on only a limited number of routes) was the TrueBlue frequent flyer program. Now they’re essentially ‘renting’ a quality frequent flyer marketing product.