The Handful Sports Bra line is a good choice because it's wire- and hardware-free, and has flat seams on the inside so it's comfortable for long flights yet supportive enough for a long run. Handful Bras are also quick-drying and could be used as a swim top in a pinch! The performance wicking lining will keep you cool and dry, and the shape is designed to flatter rather than flatten.
Use a measuring tape around your bust and ribcage and measure in inches to determine what size would fit you best. Handful can comfortably accommodate an A, B, or C cup. D+ cups can wear Handful Bras as an every day leisure, yoga and walking bra, but the higher the cup size, the more your cups might runneth over!