The first rule of Flight Club . . . is that you definitely share it with your friends. Gift frequent fliers, or infrequent shampooers, the IGK Flight Club Dry Shampoo Travel Set ($28) this season. The lightest option (Jet Lag) has finely milled volcanic ash to refresh a scalp; the style-extending Direct Flight uses turmeric to gently cleanse; and the most powerful — called First Class, naturally — uses charcoal powder for that deep detox.