WarbirdShirts Men's Cessna O-1 Bird Dog Short Sleeve T-Shirt WarbirdShirts feature a full-color profile illustration and complete aircraft specifications printed on a a high-quality, pre-shrunk, 100% cotton, 6 oz. T-Shirt. WarbirdShirts - The Gold Standard in Aviation Clothing. The perfect gift for aviation enthusiasts from nine to 90. Featured at museums and aviation sites around the world.