TwoDogs,. .. .The NZ CAA produces pilot information documents called "Good Aviation Practice" they have one titled "Wake Turbulance".. .. .On page 7 of that document they have the same photos as you are enquiring about, titled "A CX 747 -200 on approach to Kai Tak" the credit caption says "Taken from the chequerboard at a time when there was a fire in Kowloon City, thus making the vortices very visible. - Photo, Cathay Pacific 'Crews news'". .. .The document is available for download from the NZ CAA web site, the file is called waketurbulance.pdf.. .. .Regards. .. .Z