Pamplona has an airport with flights from/to Madrid-Barajas and Barcelona-El Prat. You can check the flights here
Other airports near Pamplona with international connections are:
Zaragoza is less than 2 hours drive from Pamplona. You can check the best way to come to Pamplona from this city by train or by bus in the Las Delicias station. There you'll find many possibilities to make the journey: By train or by coach. The best way to go from the airport to Las Delicias station is using the public bus (in Spanish only, sorry).
Bilbao is 2 and a half hours drive from Pamplona and many buses take you from one city to the other. There is also a bus service from Bilbao airport to the bus station where you can get the bus to Pamplona.
Biarritz in the South-West end of France, is around 2 hours drive from Pamplona. The best way to travel from Biarritz to Pamplona is by car. You can try to buy bus tickets to come to Pamplona directly from the Biarritz airport, here (to date this web doesn't work very well, sorry. Better if you try it in Spanish)
RENFE, the national railway company, is business partner of this symposium and offers participants a 30% discount on all tickets.
On the website of RENFE you can find the combination that best suits the needs of the trip to Pamplona.
You can check the web site of the Pamplona coach station to find your best choice to travel to/from Pamplona(in Spanish only, sorry).
To reach Pamplona from the biggest cities in Spain:
There's a coach service from Madrid-Barajas T4 to Pamplona (around 5 hours trip).
There's a free bus service to go from any Madrid-Barajas airport terminal to any other terminal in the same airport (green buses)
Barcelona There's a coach from Barcelona-Sants or Barcelona-Nord to Pamplona that takes around 6 hours. Too long in our opinion but it could be useful in some special situations.