< isn't 12.5K msl about where O2 is needed... might the drifting around and directional control issues be related to oxygen starvation of the brain:
If you climb above 12,500 msl but below 14,000' msl for more that 30 minutes, pilots (flight crew) must use supplemental oxygen. Anytime a pilot (flight crew) fly's 14,000' msl or above, they must be on supplemental oxygen. Since a pilots night vision is drastically effected by oxygen, supplemental oxygen is recommended during flights above 5,000' msl. Class A airspace begins at 18,000' msl where only IFR flight is permitted. Brant Hollensbe Des Moines Ia.
