Gjilan has no airport. The nearest is Pristina International Airport Adem Jashari, approximately 60 km to the west. From the airport you can take a taxi or shuttle into Pristina and then connect onwards by bus, or hire a car for the direct drive.
Buses from Pristina run frequently throughout the day and take roughly an hour. The bus station in Gjilan is central. There are also cross-border services from North Macedonia — the Kumanovo border crossing is not far to the south, and buses connect the two cities. If you are driving from Pristina, the E75 motorway takes you most of the way before dropping onto the regional road into Gjilan. The drive is straightforward and takes about 50 minutes in normal traffic.