Not a Spanish airline (I never flew on any of them, it was always Britannia, Dan-Air or British Airtours for me in the 70's and 80's), but one of my recollections of a flight to a Spanish location (LGW-ACE) was with Peach Air on an L1011.
We were due to fly (and did indeed do the return) on one of their leased Air Atlanta examples, but there was a late airframe change at LGW onto their standby aircraft, G-CEAP.
I used to fly in L1011's quite a bit in those days, more usually the military ones, but this one appeared more held together with gaffer tape than any aircraft I have ever flown in before or since. The wing upper surfaces were also covered in bird sh1t, which suggested to me it had been parked for a while. Despite appearances, and a few obvious unserviceabilities (I remember the forward hold wouldn't shut and had to be hand-cranked closed) it got us there safely.
On the return, in order for the Air Atlanta machine to make it to LGW non-stop, we had to depart from Rwy21 at ACE (it was a still, warm evening as I remember) and not towards the high ground (volcanoes) to the north of the airfield.