Why do people sometimes have a bleeding nose while travelling on an airplane?

Explanation

### Step-by-Step Solution:

1. **Understanding Air Pressure at High Altitudes**:
- When an airplane flies at high altitudes, typically between 31,000 to 38,000 feet, the air pressure outside the airplane is significantly lower than at sea level.

2. **Effect of Low Air Pressure**:
- The decrease in air pressure can lead to a variety of physiological effects on the human body. One of these effects is that the blood vessels in the nose can become more susceptible to rupture.

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