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Yes. The real risk is ink, not security. Air trapped inside the pen expands as the cabin pressure falls, and can push ink out through the nib. Travel with the pen either completely full or completely empty, keep it nib-up in your hand luggage, and do not uncap it during climb or descent.
Why a pen leaks at altitude
Aircraft cabins are pressurised, but not to sea level. The UK Civil Aviation Authority says that cabin altitude should not exceed 8,000 feet in normal operations and is typically between 5,000 and 7,500 feet. It adds that the pressure change at that level will cause any gas to increase in volume by approximately 30%.
The CAA is writing about the air in passengers' bodies, not about stationery, but gas behaves the same in a converter. The air pocket above the ink grows as the aircraft climbs, and it has to push something. The ink is the nearest thing to move, and the feed is its way out.
So the size of that air pocket decides how much of a nuisance it is. A pen with no ink has nothing to push out. A pen filled to the top has hardly any air to expand. The awkward one is the half-empty pen, with plenty of air and plenty of ink. That is the reasoning behind the usual advice from Pen Heaven, a UK retailer, which recommends travelling completely empty or completely full.
Packing the pen
Decide on full or empty the night before
If you want to write on holiday, top the pen up just before you leave. A cartridge pen cannot be topped up, so fit a fresh cartridge and keep the half-used one out of the bag. If you do not need the pen until you land, empty it, flush it and dry it, and fill it at the other end.
Keep it upright and within reach
Store it nib-up, in a jacket pocket, a pen loop or an upright pouch. Ink then settles away from the feed, and any expanding air has a shorter way to go. Pen Heaven also suggests a zip-lock bag in your carry-on for extra protection, and a cigar tube for pocket pens. A freezer bag costs pennies and will save your passport from a blue corner.
Check the cap
Screw or snap it firmly home before you leave the house. A cap that has worked loose in a bag can be the true cause of a "pressure" leak.
In the air
Leave the pen capped until you reach cruising height, then give it a few minutes before you write. Hold a tissue under the nib as you open it. Any ink that has crept into the cap or round the feed is easy to catch then, and hard to catch once it has reached your cuff.
Pen Heaven advises against writing during take-off and landing. It is good advice for your handwriting as well, because the bumps make for poor letterforms. Your fingers can warm a pen slightly as you hold it, which may also nudge the air inside it, so do not sit for long with the barrel in your fist and the nib aimed at your notebook.
What about bottled ink?
This is where rules, as opposed to physics, come in. GOV.UK’s page on liquids does not name ink, but it covers drinks, cosmetics, sprays, pastes and gels along with "any other solutions and items of similar consistency". It seems safest to treat a bottle of ink as a liquid.
The rules depend on the airport. At most, liquids must be in containers of 100ml or less, in a single clear resealable bag of about 20cm by 20cm holding no more than a litre, one bag per person. Some airports may allow containers up to 2 litres, and some do not ask for a separate bag. GOV.UK tells travellers to check every airport on the route, including connections and the return, and those rules have been changing, so look it up shortly before you travel. Bear in mind that a part-filled larger bottle still counts as over the limit.
| Carrying | Sensible packing |
|---|---|
| A small bottle in hand luggage | Check the airport's limit, then seal it in the clear bag along with your other liquids |
| A larger bottle in the hold | Tape the lid, then double-bag it and cushion it among clothes, away from anything you would hate to dye |
| Cartridges | Sealed ones in a small zip bag. They take up little room, and are often the easiest answer to the whole question |
| A journal | Keep it separate from the pen pouch, in case the worst happens |
Three small questions
- Will the pressure damage the pen itself?
- We found no good evidence that it does. The problem described by every source we read is mess, and a leak cleans up with water.
- Does it matter what kind of ink is in it?
- The physics is the same for any ink, but the consequences differ. A leak of permanent ink on a shirt is a far worse afternoon than a washable blue, so the holiday pen is a good place for a plain dye ink.
- Should I leave the good pen at home?
- That depends on what you would feel about losing it, which is a bigger risk on most trips than any leak. You could take a modest everyday pen and a travel journal, and leave the heirloom in the desk.
One honest note on sources: pen advice about flying comes mostly from retailers and hobbyists, not from aircraft engineers or manufacturers. We have kept to the part of it that follows from the CAA's figures and common sense, and you may find your own pen is more or less forgiving.