I only saw it online once as well, it was a freak thing. A high speed dive and the target pulled major G's to pull up and I overshot and saw the trails. They were on the wing tips (not roots) and I have not been able to replicate it. I tried to have somebody follow me in a dive and pull up real hard, but they did not see anything (they weren't really trying tho' -- too far out).
P.S. this wansn't "smearing" that my new LCD has, it was distinct white trails off the wing tips. Like a gas leak, but in a different spot, and it only lasted a moment. I was using a CRT back then.