Voy en avión

Several online resources and well known publications say it’s OK to use the preposition “por” to say which kind of transport you’re using to move around. Say: “Viajar por avión”, or “viajar por carro”.

I guess it’s your choice to use it or not. Personally, what I say is: “voy en avión, carro, barco o tren”.

Maybe you could use “por” if you wanted to mention where the vehicle moves on. If that’s the case then you would say something like this: "Voy por tierra, aire, agua".

I found a post about it in wordreference.

Spanish grammarHernan CortesSpanish prepositions, Transportation in Spanish, por, en