First, some background. During my second deployment I was frequently traveling. If I wasn't traveling I wasn't working. I was based out of Bagram, Afghanistan in a two person team that visited the major US Army bases to asses the information security management position of the base, write a report, and recommend changes.
Secondly, you have to understand the nature of air travel in a conflict zone. Flag officers (generals and admirals) are on a list that allows them to schedule travel so that travel works for them. For everybody else there is a space available list. Grades E9, O6, and CW5 are considered VIPs and are automatically at the top of the space available list. There are some people who have special mission clearance so they just show up and bump other people off the flight. The rest of us have to wait for a flight, often for many days. That said, you have no idea how long a travel mission will take, so you bring extra gear. You also have to understand that there are primary travel hubs and relay locations, so often there isn't a direct flight.
I would pack double the number of extra under garments for the planned travel duration and one or two extra uniforms. It gets cold in Afghanistan, so I would pack my complete triple sleeping bag sleep system (which accounts for half my personal gear) and a tiny pillow. You also need your personal hygiene stuff. You were always sure to pack personal entertainment, which for me was two novels, my laptop, and all necessary laptop accessories. Finally you also packed survival gear, which for me were additional pens, spare boot laces, spare hearing protection, a multi-tool, and some other stuff.
So, that was just personal gear that filled my large rucksack. You also needed your combat gear: kevlar helmet, body armor with kevlar plates, weapon, ammo, magazines, and any additionally needed tactical gear. You rarely actually needed any of this, but it was absolutely necessary for riding on the bird should anything unfortunate happen during travel or should you have to take a land convoy.
We still haven't gotten to mission gear. I was the lower ranking member of our two person team so I carried the gear. I carried an assault pack (standard Army backpack but tougher and heavier) with three toughbooks. A toughbook was a heavy Panasonic laptop in a thick aluminum shell tested for advanced shock protection. These things were unnecessarily stupid tough and extremely heavy. My personal laptop at the time was a small plastic netbook that I treated far worse and it proved far more durable.
All this gear added up to about 120 pounds. I discovered that when visiting Kandahar, which at that time the air terminal was run by NATO and they weighed everybody before they let you hop on a bird. I remember wearing all this stuff and leaving my living area on Bagram late for a showtime at the rotary terminal (helicopter air terminal). I miscalculated how far away that terminal was from where I was living, because the fixed wing terminal was really close. I was trying to lightly jog that nearly 2 mile route with all that gear and its the closest I have ever come to feeling like a heart attack.