Like most other airports in South Dakota, Aberdeen's airport does not have a visually impressive skyline: No tower looms where traffic controllers coordinate air travel.
But the Hub City is one of many South Dakota cities that accommodate air travel without a control tower. Of the 73 airports in the state, Sioux Falls and Rapid City are the only cities with air traffic control towers.
During cloudy weather, pilots flying in and out of Aberdeen Regional Airport are under the control of the Federal Aviation Administration tower in Minneapolis. As those pilots near Aberdeen, they switch to a radio channel that allows them to communicate with other pilots and people on the ground in Aberdeen. People who operate equipment at the airport let pilots know if they're doing snow removal or other maintenance on the runways and know to steer clear if a plane is coming in.
At one time, Aberdeen officials pushed for a control tower. But Aberdeen transportation manager Mike Wilson believes the number of flight operations in Aberdeen doesn't justify a tower.
Exact numbers aren't available, but Wilson cites one estimate that there are 128 operations, or takeoffs and landings, per day at the Aberdeen airport. Three cargo aircraft land each day, accounting for six operations. SkyWest Airlines is involved in four operations each day — two landings and two takeoffs. If a pilot does a touch and go five times, that is 10 operations.
Sioux Falls Regional Airport has 185 operations per day.
Wilson said living without a control tower is not a big deal. The lack of a tower just means that pilots and airport employees have to be more aware of safety.
“We constantly have training on how to be safe out on runways,” he said.
On overcast days, pilots rely on instrument flight rules, or IFR. Using IFR is required when visibility is no more than a mile and the ceiling is less than 1,000 feet above ground level. When flying IFR, pilots in this part of the country must remain in contact with the FAA center in Minneapolis. The FAA maintains a one-mile separation between aircraft.
A pilot flying to Aberdeen from Duluth, Minn., for instance, will stay under control of the Minneapolis center until he is perhaps 5 or 15 miles outside of Aberdeen. At that point, the Minneapolis airport will release the pilot, meaning he is clear to land.
Pilots usually then switch onto the Common Traffic Advisory Frequency, or CTAF, the channel the airport uses. With this frequency, the pilot lets the Aberdeen airport know he's coming in. He also provides specific details about his location and direction.
People on the ground may communicate with the pilot as long as he switches over to the frequency.
When skies are clear, pilots use visual flight rules, or VFR. Pilots using visual flight rules are not required to be on the radio when they approach an airport that doesn't have a tower.
So on a sunny day, some aircraft will take off and land at nontowered airports without communicating on the radio, Wilson said.
Visibility is a bigger concern in the winter. A pilot is not allowed to land unless visibility is at least a half-mile and there is a 200-foot cloud ceiling.
Rarely is a pilot not allowed to land, and the Aberdeen airport doesn't make that call, Wilson said. It's the pilot's responsibility to find out the local weather. And he is not allowed to legally land if visibility is less than a half-mile and the cloud ceiling is less than 200 feet.
Safety is a constant concern for airports. Wilson recalled that in 1983 in Sioux Falls, a snowplow was hit by an Ozark Air Lines aircraft, and the operator died.
In addition to snow removal and maintenance, workers at the Aberdeen airport perform tests. One of those tests gauges friction. If the proper standard isn't met, the airport closes its runways because they’re too slick for a plane to decelerate.