La vojaĝo per aviadilo daŭros du horojn, sed mi kunportos libron, por ke la tempo pasu pli rapide.

Per aviadilo means by airplane / by plane.

In Esperanto, per often shows the means or method by which something happens. So:

• per aviadilo = by airplane
• per trajno = by train
• per aŭto = by car
• per telefono = by telephone

So La vojaĝo per aviadilo is literally the trip by means of an airplane, which is a natural way to say the journey by plane.

The ending -os marks the future tense in Esperanto.

So:

• daŭras = lasts / is lasting
• daŭris = lasted
• daŭros = will last

Here, La vojaĝo per aviadilo daŭros du horojn means the trip has not happened yet, so the future tense is used: the flight will last two hours.

This is a very common Esperanto pattern: expressions of duration, distance, and some other measures often take the accusative -n.

So:

• du horojn = for two hours / two hours long
• tri tagojn = for three days
• kvin kilometrojn = five kilometers

In this sentence, du horojn tells us how long the journey will last.

So La vojaĝo ... daŭros du horojn means The trip will last two hours.

Yes, but the structure would be a little different.

• La vojaĝo daŭros du horojn = The trip will last two hours.
• La vojaĝo okazos dum du horoj = The trip will take place for two hours.

With daŭri, Esperanto very naturally uses the accusative of duration: du horojn.

So in this sentence, du horojn is the most direct and idiomatic choice.

Kunportos means will bring along or will take with me.

It is built from:

• kun- = with
• porti = to carry, to bring, to take
• -os = future tense

So:

• portos = will carry / will bring
• kunportos = will bring along / will take along

In this sentence, mi kunportos libron means I will bring a book with me.

Because libron is the direct object of kunportos.

In Esperanto, direct objects usually take -n:

• Mi legas libron = I am reading a book.
• Mi kunportos libron = I will bring a book along.

So:

• libro = book
• libron = a book, as the thing being brought

Por ke means so that / in order that and introduces a purpose clause with its own verb.

That matters here because the two parts have different subjects:

• mi kunportos libron — subject: mi
• la tempo pasu pli rapide — subject: la tempo

When the subject changes, Esperanto normally uses por ke + a verb in -u form.

Compare:

• Mi venis por helpi. = I came to help.
  Same subject: I came and I help.
• Mi kunportos libron, por ke la tempo pasu pli rapide. = I’ll bring a book so that time passes more quickly.
  Different subjects: I bring, but time passes.

After por ke, Esperanto uses the -u form because it expresses an intended or desired result, not a plain fact.

So:

• pasas = passes
• pasos = will pass
• pasu = may pass / should pass / pass, in a purpose or wish-like sense

In this sentence, por ke la tempo pasu pli rapide means something like:

• so that the time may pass more quickly
• so that time passes faster

It is not exactly a normal future tense. It expresses the goal of bringing the book.

Because rapide is an adverb, and it modifies the verb pasu.

• rapida = quick, fast (adjective)
• rapide = quickly, fast (adverb)

Here, the sentence is describing how time passes, so an adverb is needed:

• la tempo pasu pli rapide = time passes more quickly / faster

If you used rapida, it would try to describe a noun, not the action of passing.

Esperanto often uses la when referring to a specific, understood thing.

Here, la tempo means the specific stretch of time during the journey. So it is natural to say:

• la tempo = the time

Even though English often says so that time passes faster, Esperanto commonly uses la tempo in this kind of sentence.

Esperanto word order is fairly flexible, because endings show grammatical roles. But the sentence as written is the most neutral and natural order.

The standard flow here is:

• La vojaĝo per aviadilo — subject phrase
• daŭros du horojn — verb + duration
• sed mi kunportos libron — contrasting clause
• por ke la tempo pasu pli rapide — purpose clause

You could change the order for emphasis, but the original version is what a learner should aim for first.

The commas separate the main parts of the sentence:

• before sed = separates two main clauses
• before por ke = marks the start of the purpose clause

So the structure is:

1. La vojaĝo per aviadilo daŭros du horojn
2. sed mi kunportos libron
3. por ke la tempo pasu pli rapide

This punctuation helps the sentence read clearly and naturally.