moreover expertflyer availability might not be accurate - it's complicated, because availabilty might be different based on the point of sale - however airlines have started to use avialability based on the point of commencement for which the availability can be different again.

in January I could rebook the inbound on an O and Z fare from SIN to NUE via CDG (only two days prior to departure - moved flight from Jan 6 to Jan 2). the rebooking options shown on the air france website did not match any availability info shown on expertflyer (no matter which POS I entered).