Increasing RVSM

[Airmann]

I think it's high time RVSM airspace is increased to FL 430. A lot of airliners (and corporate jets) are capable of FL420 but this level is left empty. With talk of crowded skies and reducing fuel burn this is such an easy way of improving the overall situation.

So is there any reason why it hasn't already been done?

[wiggy]

First guess - Altimeter accuracy at 420 plus??

[DaveReidUK]

Yes, but then they would have to call it Increased Reduced Vertical Separation Minima.