Pilot meminta semua penumpang tetap tenang saat turbulensi mulai terasa.

Indonesian does not use articles like the or a/an. Whether a noun is definite or indefinite is usually understood from context.

So:

• Pilot can mean the pilot or a pilot
• penumpang can mean passenger or passengers, depending on context

In this sentence, context makes Pilot mean the pilot, and semua penumpang clearly means all the passengers.

If Indonesian wants to make something more specifically identifiable, it can use words like itu:

• pilot itu = that/the pilot
• penumpang itu = that/those passengers

Meminta usually means to ask for or to request.

In this sentence, it follows this pattern:

meminta + person + predicate

So:

• Pilot meminta semua penumpang tetap tenang = The pilot asked all passengers to remain calm

Here, semua penumpang is the group being asked, and tetap tenang is what they are asked to do.

Some useful comparisons:

• meminta air = ask for water
• meminta bantuan = ask for help
• meminta seseorang menunggu = ask someone to wait

So meminta can take either:

1. a thing being requested, or
2. a person who is being asked to do something

Indonesian often omits words that English needs, especially to in structures like ask someone to do something.

So both of these are possible:

• Pilot meminta semua penumpang tetap tenang
• Pilot meminta semua penumpang untuk tetap tenang

The version without untuk is very natural and common. It is a little more direct and compact.

So:

• meminta seseorang tetap tenang = ask someone to remain calm
• meminta seseorang untuk tetap tenang = also correct

tetap means remain, stay, or keep being.
tenang means calm.

So tetap tenang means:

• remain calm
• stay calm

There is no separate verb to be here. Indonesian often uses adjectives directly.

Compare:

• Dia tenang = He/She is calm
• Tetap tenang = Stay calm / Remain calm

Because Indonesian usually does not need a copula like is, are, or be in simple statements.

For example:

• Dia tenang = He/She is calm
• Mereka lelah = They are tired
• Cuacanya panas = The weather is hot

So in tetap tenang, tenang is simply the adjective calm, and tetap gives the sense of continuing in that state.

Yes, those are all possible, but they are not exactly the same.

• semua penumpang = all passengers
• seluruh penumpang = all passengers / the entire set of passengers
  
  • often a bit more formal
• para penumpang = the passengers / passengers
  
  • clearly plural, but does not focus as strongly on all

In this sentence, semua penumpang is a very natural way to say all the passengers.

Indonesian nouns usually do not change form for singular vs. plural.

So penumpang can mean:

• passenger
• passengers

The word semua already shows that the meaning is plural:

• semua penumpang = all passengers

Indonesian can mark plurality in other ways too, such as:

• para penumpang = passengers
• penumpang-penumpang = passengers

But in this sentence, semua already makes it clear.

Saat means when, at the time when, or as.

In this sentence:

• saat turbulensi mulai terasa = when/as the turbulence started to be felt

It introduces the time clause explaining when the pilot made the request.

Yes. All three can introduce a time clause:

• saat
• ketika
• waktu

So these are all possible:

• saat turbulensi mulai terasa
• ketika turbulensi mulai terasa
• waktu turbulensi mulai terasa

Nuance:

• saat = common and neutral
• ketika = often slightly more formal or written
• waktu = very common in speech

In this sentence, saat sounds perfectly natural.

mulai means begin to or start to.
terasa means be felt or be noticeable.

So:

• mulai terasa = started to be felt
• began to become noticeable

It suggests that the turbulence was not just existing, but was becoming perceptible to the passengers.

This is a very common learner question.

• merasa = to feel
  The subject experiences a feeling or sensation.
• terasa = to be felt, to feel noticeable, to seem/come across as

Examples:

• Saya merasa takut. = I feel scared.
• Saya merasa dingin. = I feel cold.

But:

• Getarannya terasa kuat. = The vibration feels strong / can be strongly felt.
• Turbulensi mulai terasa. = The turbulence started to be felt.

So in your sentence, the focus is on the turbulence becoming noticeable, not on a specific person doing the feeling. That is why terasa is the natural choice.

In terasa, the ter- form gives a meaning like:

• is felt
• becomes noticeable
• comes across as

It is not exactly the same as the English passive every time, but it often has a passive-like or unintentional sense.

Compare:

• merasakan sesuatu = to feel something
• sesuatu terasa = something is felt / feels noticeable

So turbulensi mulai terasa is a natural way to say that the turbulence was becoming perceptible.

Yes. Turbulensi is a normal and common Indonesian loanword, especially in aviation or travel contexts.

Because the sentence is about a plane, turbulensi sounds very natural.

You might also hear more general words like:

• guncangan = shaking, jolts
• gangguan udara = air disturbance, less common in everyday speech

But for airplane turbulence, turbulensi is the standard choice.

Yes. Indonesian word order is flexible here.

You can say:

• Pilot meminta semua penumpang tetap tenang saat turbulensi mulai terasa.
• Saat turbulensi mulai terasa, pilot meminta semua penumpang tetap tenang.

Both are correct and mean the same thing. The difference is mainly emphasis:

• first version: starts with the main event
• second version: starts with the time/background

It sounds neutral to slightly formal, which fits announcements, news reports, or written narration.

Why?

• pilot and turbulensi are standard vocabulary
• meminta semua penumpang tetap tenang sounds like a formal or official request
• the sentence is compact and smooth, like something you might read in a report or hear in a formal retelling

A more casual spoken version might be slightly different, but this sentence is very natural Indonesian.