APL- US President's own box prefix APLU, APLS (box number prefix ends with S)
CKL- Tianjin Shipping-Own Box Prefix CKLU
The box prefixes owned by CMA-CMA are ECMU, CMA, AVIC (acquisition of Zheng Li Shipping) and Anlu (acquisition of Qantas).
HAPAG- Beurotte-own box prefix HLXU, HLCU (old box coding rules do not meet international standards and will report errors).
Modern-modern merchant ships-own box prefix HDMU, HAMU
KLINE- Kawasaki steamboat-own box prefix KKLU, KKTU
KMTC- Korea Transportation-Own Box Prefix KMTU
MAERSK- Maersk Shipping-Own Box Prefixes MSKU, MRKU, PONU and POCU (Acquisition of Tiehang Slagging)
Moscow-Merchant Marine Mitsui-Moa
MSC Mediterranean shipping company
NS- Nanxing Shipping -NSSU
NYK- Japanese mail ship-niku
OOCL OOCL ulu
XYA- Xingya Shipping -HALU
SNL- Sinotrans Container Transportation Company -SNBU, SNTU
ZM- satellite transportation-zimu
CSCL- China Shipping -CSLU CCLU
Hanjin-Hanjin Shipping -HJCU
SITC- Xinhaifeng-Situ
That's all. There are many small shipowners, so I won't list them one by one. I wonder if it will help you. Not too much powder:)