733s vs 734s
Bear in mind that the Gatwick 737-436 fleet is supplemented each summer with three A319s moving down from Heathrow. With the expansion of short-haul routes at Heathrow and removal of the bmi Regional Embraer 145 at the end of the summer, BA can probably ill afford to keep sending the A319s down to Gatwick and the mixed Airbus/Boeing operation makes the crew tours immensely complicated anyway. Three of the 737-300s could well be replacements for the 319s and a fourth could sensibly be used to create a standby aircraft. This approach would only leave two as 737-436 replacements or growth aircraft , and BA does have a lot of LGW slots leased out to other airlines including Aer Lingus.