When you want to get an ad into the air, you don't have a great number of options. EasyJet uses its own planes, Nokia opted for a giant crane, and Goodyear first opted for the blimp in 1911 and has stuck with that idea ever since. 

Y&R Mumbai has borrowed the helium technology of blimps to produce a fun floating billboard to promote a low calorie sweetener. It's a nice idea that fits well with the brand, although they missed an opportunity by not making it double sided.