I'd like to know and ask whether both the sentences below are correct.
- At very high altitude you will have difficulty breathing.
- At very high altitudes you will have difficulty breathing.
My thoughts are as follows: since the word altitude has both countable and uncountable uses as described below by OALD, either will be okay and the two sentences seem to have no difference at all.
OALD's second definition for altitude(noun):
[countable, usually plural, uncountable] a place that is high above sea level, e.g. Snow leopards live at high altitudes e.g. The athletes trained at altitude in Mexico City