Achar (pickle) may not be allowed on flights primarily because of the risk of leakage.
According to the provided reference, oil, ghee, and pickle might be disallowed because:
- If there is a leak, it can stain the seats of the plane.
- Leakage can also soil the clothes of passengers.
Thus, the concern lies with the potential mess and inconvenience caused by leakage, rather than any inherent danger posed by the Achar itself.
