lets make it easier:

Tel Aviv - TLV , TA

Ramat Gan - RGN , RG

Haifa - HFA , HF

Jerusalem - JLM , JM

Rishon LeZion - RLZ , RL

Netanya - NT

Ashdod - ASH

Petah Tikva - PT

Ashqelon - ASHQ

Nazareth - NZR

Bat Yam - BY

Holon - HOL

Herzeliya - HR

Hadera - HD

Beer Sheva - BS , B7

Bet Shemesh - BSHM

Eilat - ELT

Modiin - MOD

Ra'anana - RN

Ramle-lod - RML

Kfar Saba - KF

Tverya - TVR

Ariel - AR

Katzrin - KTZ

Carmiel - CRM

Nahariya - NH

Nesher - NSH

Tirat Hacarmel - TRH

Id suggest RAG for Ramat Gan... sounds better

R.G is better like RC(COLA)