Originally Posted by javabytes

This does happen on a regular basis. I booked a flight today, one segment in A and one segment in L, all covered by the same L-UP fare. Perhaps there just wasn't A inventory for the second segment, as when I tried to get FC all the way it kicked up to a P fare. The fare rules say you get an instant upgrade if available. If it's not available, the fare can still book into the coach fare class.