Hedging
My understanding is that the ryanair hedge is to have a fixed price for a percentage of the oil needs. In effect they have bought ahead of time. Easyjet often buy caps which limits the price they pay but gives them a saving if the price drops. This cap costs money were as buying at a fixed price is cheap but does not reward the airline if the price falls. Easyjet currently has only 28% of its fuel hedged so may overall be buying fuel 10% cheaper then Ryanair until December.