If you are like me, you'll be much happier with the pillow than not.
I just flew from Hawaii to Germany, so my ears perked up when you mentioned an airline pillow. Is it the kind you keep around your neck when you are seated on an airplane but trying to get some sleep anyway? The kind that keeps it's shape even when you put pressure on it (the purpose of the pillow on the airplane, of course).
If it is, it is like my airplane pillow, and I would suggest you NOT take it.
It is too . . . "solid" , too bulky to carry in your backpack. It takes up too much space, even if lightweight. If it is a
good blow up camping/backpack pillow, by all means, use it (try it out at home first).
I won't second guess your judgement on taking your pillow. I don't know what yours is like, and if yours checks all the boxes, go for it!
In fact, every pilgrim is entitled to bring one "luxury" item with them. It might be a package of chocolate, a pillow, skin cream, whatever. If this is your luxury item, even if it is a bit heavy and bulky, you can make it work. A soft pillow at the end of the day can help your dreams drown out all the snorers around you.
Buen Camino, pilgrim!!!!