Bạn nên kiểm tra lại vé và hộ chiếu trước khi đến sân bay.

Yes, Vietnamese often leaves out the subject when it is already clear from context.

Bạn here means you, and it makes the sentence direct and clear:

• Bạn nên kiểm tra lại vé và hộ chiếu... = You should check your ticket and passport again...

In real conversation, a speaker might also say:

• Nên kiểm tra lại vé và hộ chiếu trước khi đến sân bay.

That sounds a bit more general, like One should check the ticket and passport before going to the airport or You should check... depending on context.

So bạn is included to make the advice clearly directed at the listener.

Nên means should, ought to, or it’s advisable to. It gives advice, not a command.

So:

• Bạn nên... = You should...

It is softer than an order. Compare:

• Bạn nên kiểm tra lại... = You should check again...
• Hãy kiểm tra lại... = Check again... / Please check again...
• Phải kiểm tra lại... = Must check again...

So nên is the natural choice for giving practical advice.

Kiểm tra means to check or to inspect.
Lại often means again or back.

So:

• kiểm tra = check
• kiểm tra lại = check again / double-check

In this sentence, lại adds the idea of checking one more time to make sure everything is correct.

For example:

• Tôi kiểm tra vé. = I check the ticket.
• Tôi kiểm tra lại vé. = I check the ticket again / I double-check the ticket.

Here, kiểm tra lại is very natural because people often re-check travel documents before leaving.

Vietnamese does not use articles like a, an, or the in the same way English does. It also does not normally mark plurals with something like -s.

So:

• vé can mean ticket, the ticket, or tickets, depending on context.
• hộ chiếu can mean passport, the passport, or passports, depending on context.

In this sentence, the meaning is understood from the situation: it refers to the ticket and passport relevant to the person traveling.

If needed, Vietnamese can be more specific, for example:

• vé máy bay = plane ticket
• hộ chiếu của bạn = your passport

But the original sentence is already natural and clear.

Vietnamese often leaves possession unstated when it is obvious.

In English, we normally say your ticket and passport. In Vietnamese, if the sentence is directed at you, it is already clear that the ticket and passport are yours.

So:

• Bạn nên kiểm tra lại vé và hộ chiếu...
  naturally means
• You should check your ticket and passport...

If you want to be extra explicit, you could say:

• Bạn nên kiểm tra lại vé và hộ chiếu của mình...

Here, của mình means your own. But in many everyday sentences, that is unnecessary.

Trước khi means before in the sense of before doing something.

Its structure is:

• trước khi + verb phrase

So in this sentence:

• trước khi đến sân bay = before arriving at the airport / before going to the airport

More examples:

• Trước khi ăn, rửa tay. = Before eating, wash your hands.
• Trước khi ngủ, tôi đọc sách. = Before sleeping, I read a book.

So trước khi introduces an action that happens later than the main action.

Đến means to arrive at or to come to.
In this sentence, đến sân bay means arrive at the airport or loosely go to the airport in English.

Vietnamese usually says:

• đến sân bay = arrive at the airport
• đi đến sân bay = go to the airport

Just đi sân bay is generally not correct in standard Vietnamese for this meaning.

So:

• trước khi đến sân bay literally means before arriving at the airport
• In natural English, that may be translated as before going to the airport, depending on context

Yes. Vietnamese word order is very important.

The basic structure here is:

• Bạn = subject
• nên = should
• kiểm tra lại = check again
• vé và hộ chiếu = ticket and passport
• trước khi đến sân bay = before arriving at the airport

So the order is:

subject + modal verb + main verb + object + time clause

This is a very normal Vietnamese structure.

If you move things around too much, the sentence may sound unnatural or change emphasis. For example:

• Trước khi đến sân bay, bạn nên kiểm tra lại vé và hộ chiếu.

This is also correct. It just puts the before arriving at the airport part first for emphasis.

Usually, kiểm tra lại vé và hộ chiếu is the more natural order.

In Vietnamese, words like lại often come right after the verb:

• kiểm tra lại = check again
• xem lại = review / look again
• nghe lại = listen again

So kiểm tra lại vé và hộ chiếu is the standard phrasing.

If you say kiểm tra vé và hộ chiếu lại, people may still understand you, but it is less natural in this sentence.

It is neutral and very natural. It works well in:

• travel advice
• announcements
• textbooks
• everyday conversation

Because it uses bạn, it is polite and direct without being too formal.

A more formal version might avoid bạn, depending on the context:

• Quý khách nên kiểm tra lại vé và hộ chiếu trước khi đến sân bay.

Here, quý khách is a polite way to say customers, passengers, or guests, often used in service situations.

No, not in this sentence.

Vietnamese classifiers are often used with numbers or when specifying individual objects:

• một tấm vé = one ticket
• một cuốn hộ chiếu or một quyển hộ chiếu = one passport

But when speaking generally, especially after a verb, classifiers are often omitted:

• kiểm tra lại vé và hộ chiếu = check the ticket and passport / check tickets and passports

So the original sentence sounds completely natural without classifiers.

Both can mean airport.

• sân bay is the standard and most common word, especially in modern Vietnamese.
• phi trường is also understood, but it is less common in many contexts and may sound more regional or older-fashioned depending on where you hear it.

For most learners, sân bay is the safest and most useful word to use.

The original sentence is already natural:

• Bạn nên kiểm tra lại vé và hộ chiếu trước khi đến sân bay.

Some other natural variations are:

• Trước khi đến sân bay, bạn nên kiểm tra lại vé và hộ chiếu.
• Bạn nên kiểm tra lại vé với hộ chiếu trước khi ra sân bay.
• Nhớ kiểm tra lại vé và hộ chiếu trước khi đến sân bay nhé.

These have slightly different tones:

• the original = neutral advice
• Nhớ... nhé = friendlier, more conversational reminder
• ra sân bay can sound more colloquial in some contexts

But the sentence you have is a very good standard version to learn.