I've got to book some flights between ORD and IND.
Back when I was booking between ORD and JAX, I saw that one of my bookings went into the UAL system as booking class "Y", and I got a 1.5% segment bonus.

So, I'd like to get that bonus on my trips to IND, also.
But, when I book online, I see I can select "economy", and "refundable economy". I thot booking Refundable Economy would give me the booking class Y, that I was after, but it doesn't.

Does anyone know how I book class Y, online?
FYI: Class Y, is also known as "Full Fare Economy", I believe.