Learn Hardcore Portuguese (Portugal): Eu levo só a bagagem de mão no avião.

Eu levo só a bagagem de mão no avião – completely correct.
Levo só a bagagem de mão no avião – also completely correct, and sounds more natural in many contexts.

You might keep Eu if:

you want to emphasise that it’s you (and not someone else):
Eu levo só a bagagem de mão; eles levam malas grandes.
you’re contrasting with another person:
Eu levo só a bagagem de mão, ela leva duas malas.

So: it’s optional, but not wrong. In everyday conversation, many speakers would just say Levo só a bagagem de mão no avião.

Why is the verb levo used? Could we use vou levar instead?

Levo is the simple present of levar:

levar = to take (carry something from where you are to another place).

Portuguese often uses the present tense for future plans, especially when they are fixed or habitual:

Amanhã levo só a bagagem de mão.
= I’ll only take hand luggage tomorrow.

You can also say:

Vou levar só a bagagem de mão no avião.

That sounds a bit more explicitly future-focused (I’m going to take…), but both are correct. In many contexts, levo is shorter and perfectly natural for a planned action.

What is the difference between levar and trazer? Could I say Eu trago só a bagagem de mão no avião?

Levar and trazer are direction-sensitive:

levar = to take away from the speaker’s current location.
trazer = to bring towards the speaker’s current location.

So:

At home, talking about your future flight:
Amanhã levo só a bagagem de mão no avião.
You’re taking it there (to the plane).
Already on the plane or at the destination, talking about what you have with you:
Eu trago só a bagagem de mão.
You’ve brought it here (to where you are now).

In the sentence you gave (normally said before boarding, or as a general rule), levar is the natural choice. Trago só a bagagem de mão no avião is possible, but it suggests you’re already in the context/location where the luggage has arrived.

Why is só placed before a bagagem de mão? Can I say Eu levo a bagagem de mão só no avião instead?

Só is focusing what is limited:

Eu levo só a bagagem de mão no avião.
= I take only the hand luggage on the plane (no checked bags).

If you move só, you change what is being limited:

Eu levo a bagagem de mão só no avião.
This tends to mean:
I take hand luggage only on the plane (and not in other situations / other means of transport).

So:

só before a bagagem de mão → limits the object (only that item).
só before no avião → limits the place/situation (only on the plane).

The original sentence is focusing on the type of luggage, not on where it’s taken.

Can só be replaced with apenas or somente? Are there differences in Portugal?

Yes, you can say:

Eu levo só a bagagem de mão no avião.
Eu levo apenas a bagagem de mão no avião.
Eu levo somente a bagagem de mão no avião.

All three mean only in this context.

Nuances (especially in European Portuguese):

só – most common in speech, neutral, very natural.
apenas – slightly more formal or careful; common in both speech and writing.
somente – tends to sound the most formal/literary; used more in writing, speeches, or very careful language.

In everyday conversation in Portugal, só is by far the most frequent choice.

Why is bagagem singular and feminine? In English we often say bags or luggage.

In Portuguese:

bagagem is a singular noun.
It is feminine: a bagagem.

It works like luggage or baggage in English:

a bagagem can refer to all your bags together, not just one item.

Examples:

A minha bagagem é muito pesada.
My luggage is very heavy.
Onde está a tua bagagem?
Where is your luggage?

So a bagagem de mão = your hand luggage / carry-on luggage as a category, even if it consists of more than one actual bag.

What exactly does de mão mean in bagagem de mão?

Literally:

mão = hand
de mão = of hand / by hand

In Portuguese, noun + de + noun is a very common way to form something like adjectives:

bagagem de mão → hand luggage / carry-on luggage
saco de dormir → sleeping bag
óculos de sol → sunglasses

So bagagem de mão is the fixed expression for hand luggage (the kind you keep with you, in your hand or near you in the cabin).

Could we say mala de mão instead of bagagem de mão?

Yes, you’ll hear both:

bagagem de mão – more general, can mean any hand luggage (bags, small suitcases, backpacks).
mala de mão – more specifically a carry-on suitcase (mala = suitcase).

So:

At the level of airline rules / written information:
Informamos que só é permitida uma peça de bagagem de mão.
Talking more specifically about your small cabin suitcase:
Levo só a mala de mão.

In everyday speech people mix them, but bagagem de mão is the more general / neutral airline term.

Why is the article a used: a bagagem de mão and not just bagagem de mão?

Portuguese uses definite articles much more than English.

a bagagem de mão = the hand luggage (your specific, known luggage).
Leaving the article out (levo só bagagem de mão) is possible, but it sounds less natural here and a bit more like a generic category.

Compare:

Levo bagagem de mão. – I take hand luggage (in general; feels incomplete or generic in many contexts).
Levo só a bagagem de mão. – I take only the (my) hand luggage (more natural and specific).

When you talk about your own, concrete luggage in a specific trip, a bagagem de mão is the usual form.

What does no in no avião mean exactly? Why no and not em o?

No is a contraction:

no = em + o (in/on + the, masculine singular).

So:

em
- o avião → no avião (on/in the plane).
em
- a mala → na mala (in the suitcase).

This contraction is obligatory in standard Portuguese: you don’t normally say em o avião, you say no avião.

Why is it no avião and not de avião, if in English we say by plane?

Both are possible, but they say slightly different things:

no avião = on the plane / in the plane (physical location).
Eu levo só a bagagem de mão no avião.
Emphasises what you have with you on the aircraft.
de avião = by plane (means of transport).
Eu vou de avião. – I’m going by plane.
Viajo sempre de avião. – I always travel by plane.

If you say:

Eu vou de avião e levo só a bagagem de mão.
I’m going by plane and I only take hand luggage.

So no avião fits well because we are specifically talking about what you have on board.

Can we move só to say Eu só levo a bagagem de mão no avião? Is there a difference?

Yes, that word order is also correct:

Eu levo só a bagagem de mão no avião.
Eu só levo a bagagem de mão no avião.

In most everyday contexts, they will be understood the same: you only take hand luggage.

Subtle nuance:

Eu só levo a bagagem de mão no avião. – puts a bit more focus on the whole action (“The only thing I do is: take the hand luggage on the plane”).
Eu levo só a bagagem de mão no avião. – puts the focus slightly more on what you take (only the hand luggage).

In practice, both are very natural and commonly used; many speakers wouldn’t feel any real difference here.

Is this sentence specifically European Portuguese, or would Brazilians say it the same way?

The sentence itself is perfectly fine in both European and Brazilian Portuguese:

Eu levo só a bagagem de mão no avião.

The main differences would be in:

Pronunciation – vowels are more reduced in European Portuguese.
Style – in Brazil, people might slightly prefer Eu só levo a bagagem de mão no avião, but Eu levo só… is also common.

Vocabulary and structure (verb levar, bagagem de mão, no avião) are standard and shared by both varieties.