If I did not present my membership number when I booked and checked in, is it still possible to use my flight?

A retro-credit procedure is planned for this purpose. All you need to do is provide your ticket number to receive it. You can apply for a back-credit in your personal space on the www.flycorsair.com site, in a Corsair branch or on our dedicated line within 6 months of the flight concerned.
The same applies, if you signed up after your trip, flights less than 6 months old may qualify for a credit.