1. Given data

• Mass of aircraft: $m = 5.4\times 10^5\,\text{kg}$
• Total wing area: $A = 500\,\text{m}^2$
• Speed of aircraft: $v = 1080\,\text{km/h} = \dfrac{1080\times 1000}{3600} = 300\,\text{m/s}$
• Air density: $\rho = 1.2\,\text{kg/m}^3$
• $g = 10\,\text{m/s}^2$

2. Lift required for level flight

In level flight, lift balances weight:

$F_L = mg = 5.4\times 10^5 \times 10 = 5.4\times 10^6\,\text{N}$

Hence the required pressure difference between lower and upper surfaces is

$\Delta P = \frac{F_L}{A} = \frac{5.4\times 10^6}{500} = 1.08\times 10^4\,\text{Pa}$

3. Apply Bernoulli’s principle

Let the air speed below the wing be $v$ and above the wing be $v+\Delta v$.

Then,

$\Delta P = \frac12 \rho \left[(v+\Delta v)^2 - v^2\right]$

Since the fractional increase is expected to be small, neglect $(\Delta v)^2$:

$\Delta P \approx \frac12 \rho (2v\Delta v) = \rho v\Delta v$

So,

$\Delta v = \frac{\Delta P}{\rho v} = \frac{1.08\times 10^4}{1.2\times 300} = \frac{10800}{360} = 30\,\text{m/s}$

4. Fractional increase in speed

$\frac{\Delta v}{v} = \frac{30}{300} = 0.1$

In percentage,

$0.1\times 100 = 10\%$

5. Check options

• A: $16\%$ — incorrect
• B: $8\%$ — incorrect
• C: $6\%$ — incorrect
• D: $10\%$ — correct

Therefore, the correct answer is D.