Well...According to the table:
FL 90 is 9 000ft higher than 0
, but it's not a point...
Ah shoot! Shouldn't do these things after a red or three. I'll fix the original.
If I understand correctly FL -90 is 1000 ft below 0? Sorry, I am not a pilot, so is it an option of all altimeters to show -9000 ft Altitude [FL-90] below 0? And could it be more to the negative side...for example FL-80,-70... or what ever... Will it be processed by transponder and presented by Automated ATC system?
Yes, FL -90 is 1000ft below FL 0. I'm not a pilot either & in Oz we stop at FL110. FWIW negative altitudes are displayed on our system, although I suspect it counts backwards as you'd normally do, as in 100ft below A000 shows as -001.