The F-1B Flight Trouser and Its History

The Type F-1B is the US Air Force's extreme cold weather flying trouser, built to keep aircrew warm and working when the temperature drops far below freezing. The design dates to the 1950s and stayed in service for decades, worn on flight lines and at frigid static posts where crews had to stand and work in the cold for hours at a time.

It was issued as the lower half of a layered arctic ensemble, most often paired with the N-3B and N-2B parkas. Rather than replacing your pants, the F-1B goes on over them as an insulated outer shell, which is why it cuts high on the body and opens with a full leg zipper.

Construction and Materials

The shell is a tightly woven cotton and nylon Oxford with a water repellent, windproof finish that sheds snow and blocks wind in dry cold. Inside is 100% polyester batting over a soft cotton twill lining, and that combination is what gives the trouser its warmth. The knees and seat are reinforced to take abuse.

A brass zipper runs the length of each lower leg so you can pull the trousers on over boots and vent heat when you are moving. Side hip zippers give pass-through access to the pockets of whatever you are wearing underneath. There are hook-and-loop pockets front and back, rib-knit ankle cuffs to seal out snow, an adjustable strap at the rear waist, and buttons for suspenders to hold the high waist in place. The color is the familiar military sage green.

Out in the Cold

The F-1B has found a long second life outside the service among people who work or play in serious winter. Ice anglers and snowmobilers favor the high, wader-style cut because it covers the lower back and kidneys, where cold usually creeps in first, and the full leg zippers let you get them on over boots without unlacing anything.

Hunters sitting still in a stand and workers on cold job sites reach for them for the same reason aircrew did: they trap a lot of heat in a layer that simply pulls on over regular pants. Because the shell is treated for dry cold rather than rain, they are at their best in snow and wind, not in a downpour. For surplus money, you are getting insulation and reinforced construction that would cost several times as much from a civilian snow-pant brand.

Sizing and Fit

The F-1B is cut to sit high, near the navel, and to fit as an outer layer over other trousers, so it wears roomier than a standard pant of the same waist size. Waist sizes are marked in inches. Because military sizing does not match civilian sizing, please use our Sizing & Condition Guide at the bottom of this page before choosing your size.

Quick specs

• Type F-1B USAF Extreme Cold Weather flight trousers, issued in good used condition
• Cotton and nylon Oxford shell with a water repellent, windproof finish
• 100% polyester insulation over a cotton twill lining
• Full-length brass leg zippers for easy on and off over boots and for venting
• Reinforced knees and seat, rib-knit ankle cuffs, adjustable rear waist strap
• High wader-style cut with suspender buttons, worn as an outer layer over regular pants
• Sage green, genuine US Air Force issue