The closest airport is Marseille-Provence (MRS).
There’s an airport shuttle bus (line 40) connecting to Aix-en-Provence. Travel time is about 40min. to the central bus station; buses run every 30min. for 8.60€ one-way (13.80€ return).
It is also possible to connect to the airport of Nice (NCE); the bus trip takes about 2hrs. and costs about 25€ one-way.
The Aix TGV station is on the line to Marseille and can be reached from Paris in about 3hrs.
The airport shuttle bus (line 40) mentioned above also connects the TGV station to Aix-en-Provence. Travel time is about 15min.; buses run every 15min. for 4.30€ one-way (6.90€ return).
If you are connecting to the ICALEPCS conference, there are two public transport options: