CWU stands for Crew, Warm Weather Uniform, the designation used by the U.S. military for aviation crew outerwear. The CWU-45P is the cold weather variant, originally developed for combat pilots who needed a warm, water-repellent jacket that fit inside cockpits without restricting the upper body movement required for flight controls. The 45P designation identifies the specific cold weather construction standard. The Rothco CWU-45P reproduces this aviation jacket using the same nylon water-repellent outer shell and insulated construction of the original military specification.

A bi-swing back is a tailoring technique where additional fabric panels are sewn into the back of the jacket at the shoulder area, allowing the back to expand during arm and shoulder movement without pulling the front of the jacket out of position. In a flight jacket context, this allows pilots to reach forward, operate overhead controls, and move their arms across the cockpit without the jacket riding up or restricting range of motion. For everyday wear, the bi-swing back means the jacket moves naturally with the body during any overhead or reaching movement rather than pulling tight across the shoulders.

The poly fiberfill insulation in the CWU-45P provides meaningful warmth appropriate for approximately 30°F to 50°F during moderate activity. The 100% nylon water-repellent outer shell adds wind protection that extends the comfortable range below what the insulation alone would provide in still air. For sustained sub-freezing temperatures below approximately 20°F, layering a thermal mid-layer such as the Rothco Gen III Level 3 ECWCS Fleece Jacket underneath significantly extends the system's cold weather capability.

The CWU-45P is available in sage green and black. Sage green is the authentic military aviation colour, the shade used for U.S. military flight suits and aviation crew jackets. Black provides a more civilian and law enforcement-appropriate appearance. For buyers who want the authentic military aviation look, sage green is correct. For law enforcement, security, and professional environments where a more neutral appearance is appropriate, black is the better choice.