In message , at 20:19:05 on Thu, 6 Jul 2017,
John Levine remarked:

PS: fun fact: the Heathrow web site says about passenger counts:

* Daily average total number: 206,800 (51% arrivals / 49% departures)

Who are those 4136 people a day who arrive but never leave? Does this
have something to do with brexit?

It's complicated by the fact that they are probably double-counting
transit passengers, each one being logged as both an arrival and a
departure. So if I flew Paris-London-Longhaul-London then stopped over
using a different airport or Eurostar to get back to Paris, I'd skew the
stats.
--
Roland Perry