Racedo, having dealt with most car rental groups over the years, i think its fair to say that Hertz are a reputable business from an ethics point of view, they would not bin a long term agreement with Ryanair at short notice without very good reason and having taken legal advice.
Likely a gungho response from someone rather than a well thought out plan.
Legal advice generally is to issue grievance and give a clear time line to allow other party to resolve it. It then allows a withdrawal but clear intent has already been established and cover yourself from a legal persepctive. Lawyers on both sides will get rich on this.
I dropped a car off at an airport tonight and they said Summer will take care of itself but they expect volumes to drop, however from September onwards he is forecasting 15-20% minimum drop in business and that was feeling lucky. It means he expects to lose 3-5 people minimum. At some airports that are wholly reliant on Ryanair he said it was likely that the operation would close. He was not happy and felt Hertz had stitched him up.
Something I did not know was that many of the people who check the cars in are "classified" as self employed rather than employees.