I can confirm what previous posters have said. No need to worry about your flight being cancelled
as long as you check in online for BSL-ZRH(-MAN) (actually it will be
ZDH-ZRH on a LX 74xx flight no.).
I have done it before for the purpose of getting additional miles - and sometimes you even get cheaper prices booking ZDH-ZRH-XXX instead of ZRH-XXX.
More information regarding the Airtrain can be found here:
Link