Originally Posted by xliioper

It's probably just looking at your booking class to designate cabin (rather than actual seat) and OI is a FC award booking class on equipment with FC cabins. The OI class means you are entitled to an FC seat (should one open up) as you are booked in a FC booking class on flight. You would be ahead of anyone looking for a comp FC upgrade or someone on standby waitlist who has not been confirmed as booked on flight.