"When I travel by plane I always take a few books"

Does this make sense:
cuando estoy viajando para avion estoy tomo unos libros siempre

I'd get rid of the present perfect tense and just make it present. No estoy. I might also use llevar - what do the native speakers think? And change the word order.

Cuando viajo para avion, siempre llevo unos libros.

Looking at this again....

Is it more idiomatic to say: por or en avion instead of para?

I'm not a native speaker but I hope you'll trust me...
Cuando viajo en avión siempre llevo (conmigo) unos libros.
Para is definitely not correct, por is correct but I would not use it in this situation, nevertheless I think that in Latin America it would be considered ok (sorry, my Spanish is definitely European!).

Thanks, Giulia. That's what I thought. I haven't studied Spanish for a long, long time, but, intuitively, I thought that "en" felt right.

thanks so much guys!!!