The airport Stuttgart lies about 25 km from the NeckarPark. Dependig on the traffic situation travelling by car or taxi should take about 30 mins.
You can use public transport from the airport. Take the metropolitan rail (S-Bahn) no. S2 or S3 in direction 'Stuttgarter Hauptbahnhof'. Continue one stop further to the stop 'Bad-Cannstatt'. From here it is just 1 km to the Porsche-Arena.
Traveltime is just over half an hour. From the airport in direction of the main station the trains run from 5.08 to 0.08 o'clock.
You can reach the airport by car via the exits no. 58 on the A8 or the exit on the B27.
Link - Airport Stuttgart