[bengali3]

Also there were over land speed limits applied. Apparently while at BOS you could hear the boom as the JFK-LHR flights accellerated once far enough off the coast

[vegabook]

A far better measure is the London-NY time record comparison. 777-200 did it in 5.27 hours on Jan 15 (http://www.telegraph.co.uk/news/worldnews/northamerica/usa/1...).

Concorde record was 2.88 hours (2h 53 minutes).

Ratio = 1.83:1. Much higher than the confusing Sydney comparison (1.25:1) with its stopovers.