The EI partners credit only against a very very limited selection of fare classes, and most EI fares up to about 3 weeks in advance fall in to this catergory - be warned and do your homework! It's not immediately obvious how to find the fare class on aerlingus.com so heres their instruction:
Originally Posted by aerlingus.com
To identify your booking class before purchase click on 'Terms and Conditions' during the reservation process. You will then be presented with a window and the fare basis codes will be displayed at the bottom of the page. Your booked class is the first letter of the sequence. In the example below, 'K' is the outbound class and 'V' is the inbound class.
Fare Basis Codes:
KWOWLHR - EI158
VXOWLHR - EI165