Question

Why it is not allowed to take gel pen in aeroplane.

Answer 1

Airlines sometimes just discourage you from taking gel pens on flight.

The reasons are the following:

• the air pressure in a pressurized aircraft is lower than the air pressure at the surface where you last used the pen;
• if the cartridge or reservoir are not full, there is air trapped in them, and that air is at surface pressure (higher pressure than cabin at altitude);
• if the pen cap makes a good seal, when you open the cap you will expose the feed to cabin pressure; pressure in the cartridge will then equalize by pushing air out of the cartridge, and ink with it;
• that typically results in major inkage of persons and belongings.