Maybe a practice auto-land without CAT3 runway protections and someone was given a conditional line-up behind him. I remember seeing this a few years ago at LGW when a 757 was doing one and a 747 lined behind just as he was in the flare. Became quite exciting for a short while!
Somewhat off-topic question from SLF: Do I read this right that in a CAT3 auto-land, another airplane lining up distorts the signal enough that it can become exciting? I am not 100% clear how the system works once on the ground - is the sender at the touch down end of the runway and therefore, a hunk of metal lining up is essentially the equivalent of a truck right in front of my favorite radio station?
Thanks