In very humid conditions, the turbulence caused by the aircraft itself can cause moisture in the air to condense, and hence freeze. This happens in areas of low pressure above the wing, and in the wingtip vortices, so you can get what looks like a solid sheet of contrail from the wing, and thin streamers from the wing tips (and maybe the tail), combined a bit further back with the engine contrails, as in the photo on the right. These low-pressure wing contrails can form at any altitude, given the right humidity, and account for the tales of planes landing “still spraying”