If you live near Charlotte, you’ve probably heard and seen the big, gray-painted military cargo planes rumbling low overhead. They are the N.C. Air National Guard’s C-130s, and they have been a familiar sight over the Queen City for more than four decades. That could change soon, though, as part of a military restructuring proposal that has gotten considerably less attention than the withdrawal of C-130s from Ft. Bragg.

In February, the Air Force released its proposed force structure plan for the coming years. It includes a significant change for the N.C. Air National Guard 145th Airlift Wing. Under the proposal, in fiscal year 2018 (that begins Oct. 1, 2017), the unit, which flies out of Charlotte Douglas International Airport, would transition from the C-130 to the larger C-17.

While both the C-130 and C-17 are cargo aircraft — that’s what the “C” stands for — they serve very different roles. The turboprop-powered C-130 is the U.S. military’s standard tactical transport plane, acting as a sort of a large flying delivery van for regional deliveries. The C-17, meanwhile, is a strategic jet transport, capable of hauling larger payloads, such as a tank, or a larger number of troops, over greater distances.

The transition to the C-17 is particularly notable as the N.C. Air National Guard is one of only four C-130 units that are trained to engage in aerial firefighting, which involves dropping retardants on forest fires from very low altitude, often over rough terrain. The other three squadrons are based in the western United States. C-17s are not used for aerial firefighting.

The 145th Airlift Wing is a long-time C-130 operator, having flown the type since the early 1970s. Despite this heritage, the Air National Guard’s leadership pushed for the move to Charlotte of the C-17, says Maj. Paul Kurts, spokesman for the 145th.

Kurts says the 145th’s good reputation played a critical role in the selection of Charlotte to convert to the C-17.

“The Air Force decided that Charlotte could best handle the mission,” Kurts said, noting the unit’s geographic proximity to the many military bases in the Southeast, good relationship with Charlotte Douglas International Airport, and success in recruiting personnel.

The C-17s that the N.C. Air National Guard would receive would be older aircraft and come from Charleston Air Force Base in South Carolina.

The Charlotte unit’s conversion would not require any new infrastructure spending. The guard has enough ramp space to park the eight C-17s it would receive and its existing hanger is large enough to accommodate a C-17.

The transition also isn’t expected to have much impact on the total number of people assigned to the air wing. The switch in aircraft type may lead to some turnover, however, as some long-serving troops may see this as a good time to retire while others may wish to stay on the C-130 and transfer to Air National Guard or Air Force Reserve units elsewhere.

The Charlotte unit’s move to the C-17, subject to congressional approval, comes as the Air Force is downsizing. In 2015, the Air Force had 318 C-130s, and only a third of them served with the regular Air Force. The Air National Guard and Air Force Reserve operated the other two-thirds. By 2019, the Air Force would like to reduce its C-130 transport fleet to 300 planes, with guard and reserve units retiring older aircraft.

Even so, the Air Force simply can’t close domestic bases. Doing so would require another round of Base Closure and Realignment Commission actions, something that Congress has been unwilling to authorize. So the Air Force must move planes around, being careful to give reserve and guard units something to do at facilities like Charlotte not situated at active-duty Air Force bases.

Ft. Bragg’s 440th Airlift Wing, an Air Force Reserve unit, also had operated the C-130. Under an earlier force realignment plan, the Air Force proposed closing the unit. The state’s congressional delegation is continuing to fight the elimination of the 440th.

The Air Force’s new force structure proposal also would see Air Force Reserve units in Niagara Falls, N.Y., and Pittsburgh trade the C-130s they operate for an equal number of KC-135 tankers and C-17s, respectively. The Alaska Air National Guard also would lose its C-130 squadron but assume control over the eight active-duty C-17s currently based in the state.