Why do you keep banging on about battling around in the 20's. the 250 and 350 go straight to F350.
As a former B200-driver and with no intentions to enter this willy-waggling contest, I very much doubt it happens THAT often and THAT quickly. In EU at least. RVSM restrictions and implications spring to mind...
FL280 was the best we could aim for.
DK
