The best thing to do is telephone the Servisair office at the airport you're applying for and ask to speak to the passenger service manager, who will be able to tell you if the company is looking for zero hour staff at that base. I was under the impression they didn't hire zero hour staff "off the street" rather they had to have been working for the company for at least a season before they were able to move to zero hour contracts, but I could be wrong.