Keeping the engine under the wings, doesn't hurt the lift as the airflow speed is higher under the wings?
To create a lift, the airflow speed on top of the wings should be higher than the airflow speed on the bottom of the wings.


No, that's not true.

In order to create lift, the pressure on top of the wings must be lower than the pressure on the bottom of the wings. The airflow speed doesn't matter.

I'm guessing your thought process is something like this:


To create lift, the pressure on top of the wings must be lower and the pressure on the bottom must be higher.
According to Bernoulli's principle, faster moving air has lower pressure and slower moving air has higher pressure.
Therefore, to create lift, the air speed on top must be faster and the air speed on the bottom must be slower.


However, point 2 here is wrong. Bernoulli's principle does not say that faster moving air has lower pressure. What Bernoulli's principle says is that given two points a and b, if


the fluid flow is steady, and
the fluid flow is incompressible, and
viscosity is negligible, and
gravity is negligible, and
the points a and b are on the same streamline, and
the fluid is moving faster at a than at b,


then the fluid has a lower pressure at a than at b.

Since the air above the wing and the air below the wing are not on the same streamline, Bernoulli's principle doesn't tell you anything about the speed of the air going above and below.