Is the word avião the same in Brazilian and European Portuguese?

Yes.

The word "avião" is identical in spelling, meaning, and grammatical function in both Brazilian and Continental Portuguese. The only differences are phonetic, specifically in the pronunciation of the nasal diphthong "ão" and the subtle variations in vowel resonance between the two dialects.

Brazilian Portuguese

1. O avião vai decolar em breve. (The plane will take off soon.)
2. Eu gosto de viajar de avião. (I like traveling by plane.)
3. O avião é muito grande. (The plane is very large.)
4. O avião pousou com atraso. (The plane landed with a delay.)
5. Você viu aquele avião passando? (Did you see that plane passing by?)

Portuguese (Portugal)

1. O avião vai levantar voo em breve. (The plane will take off soon.)
2. Eu gosto de viajar de avião. (I like traveling by plane.)
3. O avião é muito grande. (The plane is very large.)
4. O avião aterrou com atraso. (The plane landed with a delay.)
5. Viste aquele avião a passar? (Did you see that plane passing by?)