If you have saved the image ie the jet against a solid coloured background then just use the wand to select the background then go to the selection menu & select "inverse".You should then be able to copy the jet & paste it onto a new clear layer.Load your Jpeg or whatever & copy & paste it over your background. A little tip before pasting the Layers together make sure the jet image layer is selected go to the layers menu -matting-defringe.This helps blend the top image with the background.