This is from a Permanent Ryanair's Contract of Employment issued in Oct 06
20. Excess Capacity
20.1 Because of the uncertainty of the airline business circumstances could arise where Ryanair has excess capacity. If required to reduce our activity level for any reason, it is a condition of this job offer that you accept the right of the Company, at its sole discretion, to give you compulsory unpaid leave for the duration of the period of excess capacity or to terminate your employment.
I expect that people signing this contract didn't envisage market conditions as they are today