Dortmund Airport is served by easyJet and Ryanair. It's about 12km east of the city centre. The AirportExpress bus to Dortmund's Hauptbahnhof leaves hourly from outside the terminal (€8.50, 25 minutes).
There are frequent ICE and IC trains in all directions and RE and S-Bahn trains to other Ruhrgebiet cities departing every few minutes. The Hauptbahnhof is on the northern edge of the partly pedestrianised city centre.