Good morning YYZ_Flyer -
I believe Industrial Patent simply misposted his reply - no worries, it happens to all of us at some point or another...lol
In answer to your question regarding "mileage runs" - they are a way for people to earn miles quickly in order to achieve or maintain their current frequent flyer status with a carrier.
Perhaps at times it is "aimless" travel, however, some of the runs are planned destinations that a person may want to visit.
Some of the runs are usually long trips such as (for example) SFO-SIN, these are trips where huge amounts of miles are accrued due to the distances.
Any the who, I hope this has helped you and answered your question.
Be well & Blessings all around,
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Patrick A. Inouye, CMT
volunteer trip reports moderator