I've bought 'H' and 'B' class semi-flex fares (on domestics) before and not been allowed to change on the day, despite there being plenty of available seats. BA were only selling 'R' fares on the day, which I must say always seems to be the case. So, if 'H' and 'B' domestic fares don't seem to be available on the day, how exactly is one supposed to utilise the benefit of a semi-flex ticket? Is it all just a big con?
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DPW, welcome in particular to the British Airways board. It's great to see new people joining up with us here, so thank you for the question. As indicated the fare rules will indicate the semi flex nature rather than the fare buckets H/B etc but the fare buckets are useful in terms of a having a free transfer or not for other tickets. At H level I would normally expect at least some flexibility.
Having said that, I've looked at LHR to NCL and to EDI for travel today, a busy Friday. NCL there is no H available today, there aren't so many services, they're looking quite full and it's now showing Y9 H0 for all services. EDI is more complex, but the evening flights are filling up, but there is some H available (e.g. the very late BA1464 - a 767 at 20:55 and unpopular with weekly commuters, is showing:
J9 C9 D9 R9 I9 Y9 B7 H3 K2 M0 LC VC NC QC OC SC G1
The G1 tells me this flight is not full by any means.
So in short, you need to be careful with tickets other than semi flex. If ticketed in Y, it is probably OK, but won't be cheap normally, but if at B and below is probably best for mid week, middle of the day travel on less busy services.
When BA says R only, it's typically in the final hour before departure, it's not routine for further out.