Question

why do cells lining the air passages of a human body have a lot of mitochondria and cilia

Answer 1

To trap fine dust and dirt particles that might enter the passage and harm the body. They're like filters, somewhat. :)

Answer 2

to add to Student's answer, the mitochondria are also there because the air passage would be rich in oxygen, which allows the mitochondria to perform cellular respiration breaking down glucose into CO2 and H20 creating ATP for the cells to use.