A marginal one really... I'm now running three types, Beechraft 99 Series, HS 748 Series and 727-200 Advs. To be honest the Beechcraft have been something of an experiment out of curiosity following the Swiftus Small Airline Test, also inspired by a decreasing number of route options out of my base.
On balance I think I'm actually making a slight overall loss on the Beechcraft, but only becuase of being in three types. I reckon if I was operating only Beechcraft and HS 748s the Beechcrart would in themselves be profitable. They do three or four routes each a day, and don't fly 00-06hrs as my base is closed and the 23-00hrs/06-07hrs slots are in demand for my larger a/c.
I'm not 100% sure, but I think there is a slight economy-of-scale with staffing, I haven't found I need many more staff other than aircrew and ground handlers adding the Beechcraft operation.
They are only on one year lease, so if they cause me drama I'll probably axe them, but I'm hoping to buy them out if they do OK, getting 2mil odd a go for them is easy enough, and I can then have an asset base to back expansion. I'm still trying to get hold of a couple of C99's for the extra seat and hopefully to replace the aging B99's.
Anyway, having started a couple of years late in my first game, I'm happy my second-ever airline is moderately sucessful, and am taking the chance to try a few ideas out for my first full-length game in the Spring. I've found running a very effecient schedule to be a big help, even with 8 of 36 a/c not flying at night I'm still the 15th-highest fleet utilisation player.
Edit: Lots of typos...