My niece and nephew flew in from Europe three weeks ago with a 3 month old who is being nursed to attend our daughter’s chasunah.
They were on Swiss non-stop from Zurich. Niece discussed it with the stewardess and was given 2 options for nursing with privacy. In non-meal periods they’d let her use a jump seat in the galley and close the curtains while blocking access with a cart. During meal periods she would be permitted to use the lower level crew rest area (this was on an A330 Jet). It worked out that she used the galley 3 times during the flight.