There's argument posted on this forum very often about some routes, which UA keep flying despite light or moderate pax loads, because they are cargo-profitable.
I'm not familiar with the subject, but IIRC cargo is a profitable business for UA. Perhaps someone could enlighten me and other FFT-ers about geography of such routes.
Another question I'd like to ask is, why then UA does not have in their fleet 744 Combis, which probably could be suitable to serve such routes or deployed on routes where smaller planes fly with full cabins, but can't take more cargo?
After all many airlines use the Combis successfuly for many years, so why not UA?
IIRC, there was also version called Convertible where back section could be converted from pax cabin to cargo and back.