This is something which catches most of us at some stage. You are flying merrily along, steadily gaining height and suddenly… “oops” … I must have flown into an eclipse… Everything has gone dark… what did I do wrong now? you ask yourself. Is my PC overheating? … something has gone badly wrong…
No nothing has gone wrong. You are flying a simulator which actually simulates … You need Oxygen… Hypoxia…
You can turn the effect off by un-ticking the checkbox in the Settings –> General page