Is this the 09:40 departure (BA 938)?

If so the inbound aircraft is usually the 07:15 MAN-LHR (BA1385) and this has been a 321 the last couple of times I have used it on a Monday.

I met a colleague in LHR recently and then we both flew on to an exhibition in DUS and I ended up boarding exactly the same plane I had just left

The BA electronic timetable lists the BA938 and BA1385 as an A321 on Mon and Tue only with an A319 the rest of the week.

Hope this helps

Signed

Bad Attitude