There are still some floating around on other airlines - e.g B6 777 BOS-LAS, B6 669 JFK-SJC (San Jose area code 669), KL 617 AMS-BOS (Boston area code 617), AS 412 SEA-PIT (Pittsburgh area code 412) - but a lot of them have been eliminated as this era of having too many flights to do a consistent numbering scheme around, especially in the US.