Answer:
Probably because the Bernoulli effect (lift) is insufficient in thinner air to keep the plane aloft - increasing the angle of attack will increase the lift on the airplane
Answer:
Rise in level of fluid is 0.11 m
Rise in level of fluid in case of mercury is 0.728 cm or 7.28 mm
Solution:
As per the question:
Density of oil, 
Change in Pressure in the tank, 
Density of the mercury, 
Now,
To calculate the rise in the level of fluid inside the manometer:
We know that:
1 mmHg = 133.332 Pa
Thus

Also,

where
g = acceleration due to gravity
h = height of the fluid level

h = 0.11 m
Now, if mercury is used:


h = 0.00728 m = 7.28 mm
If it i hot it makes it easy to clean