If the comment above is accurate then the airliner pilots involved are very brave. Gransden Lodge is a notified cable launch site to 3,000' above surface (250').
Well, I've grabbed a snapshot of the Atlantic Airlines track off RadarVirtuel website. Jim59. I'm not sure that it's going to work as a link.
I'm not sure that "brave" is a good way to describe this sort of flight path. He/she might have considered it safe because it was late on a Saturday afternoon. Perhaps Stansted had ascertained that gliding had finished for the day, but I really don't think that an airliner should be there.
BoW
Picasa Web Albums - cmacdb - Airliner tracks