Decision of the EU Court of Justice, 7 September 2017: “…The compensation payable to passengers in the event of cancellation or long delay of a connecting flight must be calculated according to the radial distance between the departure and arrival airports. The fact that the distance actually covered by such a flight is, as a result of the connection, greater than the distance between the departure and arrival airports has no impact on the calculation of compensation…”
Three passengers with a Brussels Airlines ticket Rome-Brussels / Brussels-Hamburg demanded 400 Euro because they flew 1.656 kms (1.173 kms + 483 kms). The court decided that compensation is 250 Euro because Rome-Hamburg is 1.326 kms.
Forum discussion: http://www.luchtzak.be/forums/viewtopic.php?p=355451#p355451