Are we talking about the Word Airways DC10-30Convertible? The 'Junk', as it is known in the industry? Well, I guess BAX's 8 got a mechanical and the junk was the only one available on short notice... But that's just a guess.
I think it was World who I saw during peak season last year who had to allow extra space on their main deck for spare parts. I couldn't believe it when I heard about it at first. An aircraft that had to carry around its own spares in case of a mechanical. I wanted to ask the pilots if they flew their mechanic in the jumpseat on all flights also.
Carrying around spares in addition to MECH/OPS personnel is a pretty common practice on airlines like Tower, Sun Country, and World who do DOD contracts to air force bases/air stations without adequate ramp/A&P staff.