In Jainism, the idea is not about “saving germs”. It is about minimizing हिंसा (violence) and avoiding foods or actions that involve a greater amount of injury or increase passions.

Why onions are avoided

Onion is avoided because:

• it is a root vegetable, so harvesting it destroys the whole plant and many living beings in the soil,
• it is believed to increase passions, agitation, and attachment,
• it is considered unsuitable for a life of sattva, restraint, and purity.

So the main reason is ahimsa and spiritual discipline, not “protecting germs.”

Why flying in a plane is not automatically a sin

In Jainism, many actions in worldly life involve some degree of harm. A householder cannot live with perfect monk-like renunciation.

Flying in a plane is generally seen as:

• not done with the intention to kill,
• usually done for necessity, duty, health, or important work,
• accepted as part of limited worldly life, where one tries to reduce harm as much as possible.

The Jain principle

Jain ethics does not say:

• “Only some violence is sin and other violence is pure.”

Rather, it says:

• violence should be avoided as much as possible,
• if unavoidable, it should be done with care, restraint, repentance, and minimum harm.

So:

• Not eating onions is a voluntary act of restraint and nonviolence.
• Taking a plane may involve unavoidable worldly activity, so it is not condemned in the same way, especially for a layperson.

In short: Onions are avoided because they are a chosen, unnecessary form of harmful food, while flying is often considered a necessary worldly act with unavoidable violence.