80 on a Saturday afternoon?
Last time I checked it was a Sunday...
I don't think it was covering for an A321. The A321 operated at 12.15. It looked like it was added to the schedule as all other flights took off at the usual times.
Not a very wise choice of A/C considering two flights either side within an hour. All other flights with 80%-90% load factor today. Slightly baffled at the choice of a 763!