Folks,
"Coming down" was an affectation of British European Airways (BEA) starting back in the 1960s, and was, unfortunately, emulated by the impressionable, in the mistaken belief, in the UK, that the British "Corporations" were the height of professionalism.
On would have thought that the heaps of scrap aluminium they (BEA and BOAC) left around the landscape in those days, might have given pause for thought on that score.
Mercifully, it is only occasionally heard in this day and age.
Tootle pip!!