Flying With Fountain Pens

When flying with a fountain pen, it's really all about the volume of ink and the orientation of the pen. The pressure changing in the cabin affects the pens, especially during takeoff and landing so during those times you'll definitely not want to be using them! There are a few pieces of advice I can give when flying with pens:

If you can, just clean them and keep them empty before flying, it's the only 100% guaranteed way to avoid an ink spill ;)
If you fly with your pens inked up, keep them stored with the nib pointed up. Any air in the ink chamber will remain near the nib this way. The reason ink leaks during flight is because the pressure in the airplane cabin drops as you leave the ground and go up into the air. This means the pressure in your pen is higher than the surrounding environment, and when that happens…it wants to equalize. There's only one place for the air to go, and that's through the nib. And if there's ink between the air in the ink chamber and the nib, then the ink is going out! So if you keep your pens pointed nib up while flying, this keeps the air bubble in the pens at the nib.
Keep your pens as full as you can if you keep them inked. Where you get into trouble is when you have some ink and a lot of air, as the more air there is in the ink chamber, the more likely it is to leak (for the reasons in #2).
The biggest risk of leakage is during takeoff. Planes don't pressurize the cabin until about 6,000ft elevation, so the air pressure is dropping rapidly from the time you leave the ground until you hit 6,000ft (or somewhere close to that, it probably varies by plane). Once you reach about 6.000ft elevation, the cabin maintains pressure at that level and you're good from there on up. Using a pen while descending isn't nearly as big a risk as the air pressure is increasing as you drop, so the ink in your pen is being forces back into the pen.
Ink bottles are fine, air pressure difference will equalize as soon as you open the top, and since the air will always be at the top when you open it, the risk of leakage is very low. You should probably be more worried about physical damage to your glass bottles due to the baggage handlers! Just be sure to pack your bottles well.

So there you go, keep them either full or empty, and keep the nib pointed up and you'll be okay :) And if you want to be really safe, put them in a ziploc bag that way if the worst happens and you do get a leak, it's contained :) Have a good flight!

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