Ryanair and Shell have agreed a memorandum of understanding (MoU) "to advance the supply of sustainable aviation fuel (SAF) at over 200 Ryanair airports across Europe", according to a joint statement.
The tie-up, they said, would entail a "particular focus" for supply to Ryanair's main hubs at Dublin Airport and London Stansted and would give the Irish airline "potential access" to 120 million gallons of SAF.
The fuel in turn would allow Ryanair cut around 900,000 tonnes of carbon dioxide emissions - equivalent, it claimed, to over 70,000 Dublin-Milan flights.
The airline's sustainability director Thomas Fowler said using SAF was "key" to its "net zero" aims and would give it access to a fifth of the SAF it aims to be using by 2030 - by when it also hopes SAF will make up 12.5% of its overall fuel needs.