Ĉiu pasaĝero devas kunporti sian pasporton al la flughaveno.

Ĉiu means each / every, so it is normally followed by a singular noun: ĉiu pasaĝero = each passenger.

If you said ĉiuj pasaĝeroj, that would mean all passengers. The overall idea is similar, but the viewpoint is slightly different:

• ĉiu pasaĝero = looking at passengers one by one
• ĉiuj pasaĝeroj = looking at the whole group together

So this sentence is phrased in a distributive way: every individual passenger must do this.

Devas is the present-tense form of devi, which means to have to / must.

So:

• devi = to must / to have to
• devas = must / has to / have to

In Esperanto, modal verbs like devi are followed by an infinitive:

• devas kunporti = must bring along

This is very similar to English must bring or has to bring.

Esperanto often builds words from smaller meaningful parts.

• porti = to carry, to wear, to bear
• kun- = with, along

So kunporti means to carry with oneself, or more naturally in English here, to bring along.

That is why kunporti sian pasporton means to bring one’s passport along.

This is slightly more specific than plain porti, which just means carry.
It suggests that the passenger should have the passport with them when going to the airport.

Sian is the reflexive possessive form. It means his/her/their own, referring back to the subject of the clause.

Here, the subject is ĉiu pasaĝero. So sian pasporton means the passenger’s own passport.

That is exactly why sian is used: each passenger must bring the passport that belongs to that same passenger.

Compare:

• Ĉiu pasaĝero devas kunporti sian pasporton.
  = Each passenger must bring their own passport.

• Ĉiu pasaĝero devas kunporti lian pasporton.
  = Each passenger must bring his passport, where his refers to some other male person, not back to the subject itself.

So sia is very important for showing ownership that points back to the subject.

Because the sentence is talking about each passenger individually, and normally each one has one passport.

So:

• sian pasporton = their own passport

If you used siajn pasportojn, that would mean their own passports, suggesting more than one passport per passenger.

The singular fits the normal real-world meaning.

The -n ending marks the direct object in Esperanto.

Ask the question: what must each passenger bring along?
Answer: sian pasporton

So pasporton gets -n because it is the thing being brought.

This is the accusative ending:

• pasporto = passport
• pasporton = passport as a direct object

Notice that sian also matches it:

• sia pasporto
• sian pasporton

Adjectives and correlatives used like adjectives also agree with the noun in number and case.

Because the preposition al already shows direction: to / toward.

So:

• al la flughaveno = to the airport

In Esperanto, when a preposition already clearly marks the role, the noun after it usually does not need -n.

That is why you get:

• kunporti sian pasporton → direct object, so -n
• al la flughaveno → prepositional phrase with al, so no extra -n

La is the definite article, meaning the.

So:

• la flughaveno = the airport
• flughaveno = an airport / airport in a more indefinite sense

In this sentence, the airport sounds natural because it usually means the airport the passenger is going to. Esperanto often uses la in places where English would naturally use the.

Also remember: Esperanto has no indefinite article. There is no separate word for a/an.

So:

• flughaveno can mean an airport
• la flughaveno means the airport

Yes. That would be perfectly normal Esperanto.

It means roughly the same thing, but the structure changes from each passenger to all passengers.

Compare:

• Ĉiu pasaĝero devas kunporti sian pasporton.
  = Each passenger must bring their own passport.

• Ĉiuj pasaĝeroj devas kunporti siajn pasportojn.
  = All passengers must bring their passports.

In the plural version, the grammar changes accordingly:

• ĉiuj instead of ĉiu
• pasaĝeroj instead of pasaĝero
• siajn instead of sian
• pasportojn instead of pasporton

Yes, to some extent. Esperanto word order is fairly flexible because endings help show what each word is doing.

The most neutral order here is:

• Ĉiu pasaĝero devas kunporti sian pasporton al la flughaveno.

But other orders are possible for emphasis, for example:

• Sian pasporton ĉiu pasaĝero devas kunporti al la flughaveno.

That puts more emphasis on the passport.

Still, for learners, the original order is the clearest and most natural: subject + verb + object + prepositional phrase.

It is a compound word:

• flug- = flight
• haveno = harbor, port

So flughaveno literally means something like flight-harbor, which is the Esperanto word for airport.

This is a very common Esperanto pattern: combining simple roots to make clear, logical words.