It was once not uncommon for the US Starlifters and Galaxies YSRI-YBAS to have their clearances denied by SY DEPs (usually due to a u/s or temperamental txpdr), resulting in them flying out to PKS OCTA. Was interesting viewing a 1200 paint with a g/s of about 90kts op direction to a C5 500' above. Would have been intimidating in the 150 or whatever it was, I'd imagine it would be something akin to a shadow falling over the sun!