Wear comfortable clothes that allow you the full range of movement for airplane travel. Clothing should cover most bare skin. Check your hiking boots or any shoes difficult or time consuming to remove, but also avoid slip-on sandals and open construction shoes, which afford little protection and that may be lost in an emergency.
Avoid nylon and synthetics, which may melt in a fire. Instead, choose natural fibers--cotton material, jeans. Do not wear clothing you have been wearing in the wilds if it could be covered in bug repellent or poison ivy.
Stow your cotton once you leave the plane. In cold or damp conditions, cotton is a killer. In the heat, it traps heat and moisture, weighing you down. Here, synthetics like nylon are your best friends.
Choose breathable fabrics. Often these either wick away moisture from your skin or allow air to circulate, letting sweat evaporate to cool your body or help retain your body heat.
Look for outdoor clothing fabrics and construction that include fast-drying, lightweight materials, ripstop fabrics (which resist tears from rocks or snags) and materials made to insulate or hold in body heat for colder weather.
Flat seams prevent chafing, especially under a pack or at points where abrasion may occur with repetitive movement. Zip pockets keep you from losing essential items. Under Armour and The North Face are two widely stocked brands that offer many of these features.
Zip away or zip off transforming clothing is great for changing conditions. Pants legs can be removed and packed during the heat of the day or for water crossings. They quickly reattach if you encounter sudden storms, mosquito or chilly temperatures.
If you cannot find everything you need in a single piece of clothing or if you expect to face changing conditions, layer your clothing. You can then remove pieces as necessary to remain comfortable and avoid sweat accumulation.