747-400C

There is no Boeing 747-400C. If you are looking for one, the aircraft you want is the 747-400M Combi.

Where the confusion comes from

The mix-up is entirely reasonable. Across the 747 family, C does mean cargo-capable — the 747-200C is a genuine variant, a Convertible that could be switched between passenger and freighter roles.

So when people encounter a 747-400 carrying freight on its main deck, “747-400C” is a natural guess. But Boeing never built a Convertible on the -400 airframe. The cargo-capable passenger -400 is designated M, for Mixed configuration, and is universally called the Combi.

The letters, straightened out

Suffix	Meaning	On the -400?
M	Mixed — passengers and freight together on the main deck	Yes — 747-400M, 61 built
F	Freighter — cargo only, factory built	Yes — 747-400F, 126 built
C	Convertible — switched between roles, seats removable	No. Only on the 747-200C
D	Domestic — high density, short range	Yes — 747-400D, 19 built
ER	Extended Range	Yes — 747-400ER, 6 built
BCF	Boeing Converted Freighter — a rebuilt passenger aircraft	Yes — 747-400BCF

The distinction between M and C is real, not pedantic. A Combi carries passengers and freight simultaneously, separated by a partition. A Convertible carries one or the other, with the seats physically removed between roles.

The nearest thing to a “converted” -400 is the 747-400BCF, but that is a permanent rebuild of a passenger aircraft into a freighter, not something switched back and forth.