I am sure a couple of years ago there were three.
Swissport Handling Agents for:
Astraeus
AtlasGlobal
El Al
First Choice
La Compagnie
Onur Air
Ryanair
Sunexpress
Thomson
VLM
Wizz Air
All cargo flights
Menzies Handling Agents for:
Blue Air
easyJet
Jet2
Monarch
TAROM
I guess that is around 50% each for passengers