Unfortunately, not with a cartridge installed...unless you like all the ink on the outside of your pen and not inside the cartridge. The lower cabin pressure will force the ink out of the cartridge and make a huge mess! If you remove the cartridge for the flight and carry sealed cartridges to use once you land, that's fine.
Check out this article: “Guide to Fountain Pen Nibs.” Typically Extra Fine (EF) and Fine (F) are the most popular. Some of this depends on how large you like to make your characters. Larger nibs also tend to write “wetter” than fine nibs. My personal preference is Medium (M) because I like a heavier line and larger letters. https://www.jetpens.com/blog/guide-to-fountain-pen-nibs-choosing-a-fountain-pen-nib/pt/760
Fountain pens require a bit more thought and technique but it's pretty simple...kind of like a mechanical pencil. Check out this article: “How to Write With a Fountain Pen” https://www.jetpens.com/blog/how-to-write-with-a-fountain-pen/pt/271
Getting the most out of your fountain pen takes a little bit of knowledge and care. If you get really into it you can even tune your nib. There are folks out there that do this for a living! Like all things manufactured, not every nib is perfect. However, there is a bunch of stuff you can check/try out to get a nib working better. Check out this article:
Guide to Fountain Pen Nibs: Troubleshooting Tips and Tricks” https://www.jetpens.com/blog/guide-to-fountain-pen-nibs-troubleshooting-tips-and-tricks/pt/777
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