Aki has signed a 3 year extension to his deal keeping him in Galway until 2020 while Dillane has signed a 2 year extension.
Aki qualifies to play for Ireland next year.
The confirmation comes within 24 hours of Joe Schmidt confirming that he'll stay on as Ireland coach until the end of the World cup in 2019.
Meanwhile, Ulster have confirmed that Iain Henderson and Rodney Ah You will miss Friday night's Pro12 encounter with Munster through injury.
In better news Darren Cave and Robbie Diack have been cleared and will be ready if required.
