How does that compare to a long-haul flight?

Flight distances are great-circle routes, which is why a map makes them look wrong. These are the real numbers.

The distance Unit

90% of London to New York

5,000 km is further than 2 of the 8 references on this page.

Reference figures are measurements and are rounded; the unit conversion behind them is exact.

Every reference on this page, with its size and its ratio to your number
Reference	Size	Yours ÷ theirs	Note
London to Paris	344 km	14.5×
New York to Chicago	1,145 km	4.37×
London to New York	5,567 km	0.898×
Los Angeles to Tokyo	8,815 km	0.567×
London to Cape Town	9,670 km	0.517×
Singapore to New York	15,349 km	0.326×	The longest scheduled flight
London to Sydney	16,993 km	0.294×
halfway around the world	20,038 km	0.25×	The furthest two points can be

Singapore to New York is the longest scheduled flight at 15 349 km and about 18 hours 45 minutes.
No two points on Earth are more than 20 038 km apart, so every flight is less than half a lap by definition.

Frequently asked

Singapore Airlines SQ23/24 between Singapore and New York JFK, 15 349 km, flown by an A350-900ULR in roughly 18 hours 45 minutes.

They do not — the map does. The shortest path on a sphere is a great circle, and flattening a sphere onto a rectangle bends those into arcs.