Why people are advised not to carry fountain pen while travelling by air?

People are advised not to carry fountain pens while traveling by air due to the potential for ink leakage caused by changes in cabin pressure during flights. The pressure difference can force ink out of the pen, leading to messy spills and possible damage to belongings. Additionally, some airlines may have restrictions on carrying liquids, including ink, which could complicate travel. It's often safer to opt for ballpoint pens or other alternatives that are less prone to leaking.