Originally Posted by
APUBleed
... I'm flying to Mykonos on what looks like a basically full flight ...
ISTR from previous discussions that LCY-JMK is never "full" in the sense that every seat on the aircraft is occupied. The aircraft is payload restricted, so BA will not book the aircraft to capacity.
If you got the impression of "full flight" from zeroes on an availability display, that's another illustration of the fact that availability displays can sometimes tell you very little about how many bodies will be on board the aircraft. Trying to work out one from the other is (as I am frequently saying here) like trying to read tea leaves.