I learned that the hard way a few years back, the ink exploded on the form I’m writing on that I had to hunt down an FA to secure me one of those forms. I had to borrow a pen from a neighbor. I had to empty my fountain pens, either carry an extra nib or a bottle of ink. Placed them in a ziplock with lots of tissue for cushion and for accidental spills.
I carry two Sarasa pens (one of those pens that works great for left-handed) for writing on the plane.