You can say this in two different ways:
1. El viaje en avión...
2. Viajar en avión... (Travelling by plane...)
I imagine you are trying to translate literally your "travelling" in English to our gerund "viajando" (travelling), but in this case we use an infinitive, not the -ando, -iendo form.
We have a useful A2 lesson explaining this. Have a look here.
I hope it is useful.
When is it "menos ... de" and not "menos ... que"?
Here is our lesson on "más que/menos que/más de/menos de".
I hope this helps.
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