As well as the leased aircraft there also seems to be the issue of flights that BA are operating without passengers. Yesterday, BBC News said that some of the "cancelled" flights from JFK may still be operating with freight only. ITV News have been told by the union that many flights have left Heathrow empty.
The flight on the network screenshot, BAW178F, was listed as cancelled on ba.com, baa.com and flightstats.com, but here it is with a F suffix approaching the west Wales coast and also landing at Heathrow.
I guess that these flights allow BA to reposition aircraft and meet their freight commitments.