Originally Posted by
ng1265
For BSL as mentioned upthread - Mulhouse airport or Basel Euroairport - French side (Avis code MLH)
For GVA use Geneva airport - French side or Geneve airport (Avis code GGV)
No risk using the frequent flyer Elite code if you're not a member: Avis will generally monitor company codes and ask for proof of employment for those, but are not generally bothered if you use the frequent flyer codes.
That is an amazing tip! Just priced it our and it was about 45% less. Too bad there isn't another country next to Zurich airport for car rental purposes!