I see CAL are the operators of 4X-ICA which I have occasionally noted overflying UK on FR24. Odd can't recall them at all from my visits to Heathrow in 70s/80s but the I didn't go that often.
Pic here of N801FT in basic FT scheme with CAL and El Al titles... but it looks a bit odd to me, probably a Photoshopped image?