There are a minimum number of hours specified by Federal Aviation Regulations (FARs) Part 61. I don't know the average now, but the national average used to be about 20 hours over the minimum. Those students who took less than the national average were those who took 3 to 5 lessons a week (some went 7 days).
A rare but very serious risk associated with blood transfusions is transfusion-related acute lung injury (TRALI). It occurs more often with platelets and plasma than with red cells. TRALI is a poorly understood condition, in which a personâs lungs suddenly become very inflamed within six hours of the transfusion.
Transfusion is typically ordered because of the risk of anemia - which the National Institutes of Health defines as a condition where the body does not have enough red blood cells. Anemia can cause the person to feel tired or weak, have headaches and shortness of breath, as well as problems concentrating or thinking.