I worked on United's computer systems for a year (never that one though), and so I get nervous when I see a headline like that. True story: one of their systems still runs on a mainframe that has 9 bits in a byte!
I did not know that was ever a thing. I knew that bit counts had been lower - 5 or 6 - but assumed once we hit 8, the whole power-of-2 thing was too comfortable in a binary system to ever be anything besides a power of 2 again - and sure enough, we get 16 bit, 32 bit, and 64 bit systems, and double-byte and triple-byte char sets, etc. Need more space? Take another byte. Was the 9th bit special? Or just a standard bit…
36 bits got us the 6-bit character (10 digits, 26 letters, and punctuation) with six characters in a word. Because of that, some OSes had six-character file names.
If you want to get upper- and lowercase, you need more than 6 bits. 9 is the smallest divisor larger than 6 of 36, so nine-bit characters made sense.
On such systems, file names could still use 6-bit characters, while applications used 9-bit ones. Also, some instructions could work on words, half words, quarter words, or sixth words.