The huge demand for air transportation to support  Iraq operations has allowed the KC-135 tanker to operate more frequently in its secondary role as a personnel and cargo transport. The KC-135 always had space for cargo or passengers, but has rarely performed in this role. Now this is changing. Every KC-135 can carry a combination of 40 tons of cargo or 37 passengers. Currently, one of the more frequent passenger jobs has been moving wounded troops from Iraq to hospitals in Germany or the United States. The current U.S. military medical system uses what is basically a portable ER (Emergency Room) close to the combat, that promptly stabilizes the badly wounded, and then gets them on to an aircraft, along with medical staff and equipment, for movement to a major hospital. Previously, the C-9 was used for this, but this aircraft was retired in 2003. However, many of the other aircraft used for this, like C-130s, also have to make refueling stops to get from Iraq to the United States. A KC-135 can do it non-stop. So KC-135s coming back from a tour in Iraq or Afghanistan, will often carry patients, and the small ICU (Intensive Care Unit) people and equipment that used to make these flights on C-9s and C-130s. KC-135s on their way to Iraq, often carry some cargo with them. Since there is not a lot of air warfare going on in either Iraq or Afghanistan, which is what KC-135s usually support, there are many KC-135s that can be used just for cargo and passenger runs. The air force is also equipping KC-135s with communications equipment that makes them the equivalent of low flying communications satellites. Since KC-135s are built to circle the combat zone for hours, this additional communications duty (which takes the load off the real satellites overhead), is another good fit.