Hello . .
To be honestly, assigning tags or other taxonomy to 6000 posts is pain process, very risky to human error, and it would take quite long time to complete
I prefer an automation process where the tags would be assigned automatically by custom script, if you have a list of those tags & posts relation ( in csv, or other files ), or if there are certain scheme for tagging, that would be very helpful
Also, wordpress tag algorithm would detect 'Qatar airways' as 'qatar-airways' slug instead two of tags actually :)
Please let me know what you think,
Thank you and regards,
Eni