"jsmith" wrote in message ...
Domestic Reduced Vertical Separation M?? begins at FL280.
Prior to January 20, 2005, vertical separation between aircraft above FL280 was 2000 feet. As of 20 January 2005, the
vertical separation between aircraft at FL280 and above is 1000 feet. Only aircraft properly equipped for DRVSM are
permitted to fly above FL280.


Altimeter accuracy ±65' for current birds and ±130' for older ones. Pretty amazing stuff actually, something like 1/4 of
1%...