Турбулентность длилась недолго, и стюардесса спокойно попросила нас не вставать.

Длилась is the past-tense form of длиться, which means to last / to continue.

It is feminine because the subject is турбулентность, and that noun is feminine in Russian. In the past tense, Russian verbs agree with gender in the singular:

• masculine: длился
• feminine: длилась
• neuter: длилось
• plural: длились

So:

• Турбулентность длилась недолго = The turbulence did not last long

In this sentence, недолго is normally written as one word because it means for a short time / not for long as a simple adverb.

• долго = for a long time
• недолго = not for long / briefly

If you wrote не долго separately, that would usually sound contrastive, as if you were saying not long, but...

For example:

• Турбулентность длилась недолго. = The turbulence didn’t last long.
• Турбулентность длилась не долго, а всего пару минут. = The turbulence lasted not long, but only a couple of minutes.

So in your sentence, недолго is the normal choice.

There is a comma because и is joining two full clauses with different subjects:

1. Турбулентность длилась недолго
2. стюардесса спокойно попросила нас не вставать

Russian usually puts a comma before и when it links two independent clauses.

So the structure is:

• [The turbulence didn’t last long], and [the flight attendant calmly asked us not to stand up].

Стюардесса is a very common word meaning female flight attendant. It is understandable and natural in everyday Russian.

A more official or gender-neutral modern term is:

• бортпроводница = female flight attendant
• бортпроводник = male flight attendant

But стюардесса is still widely used in normal speech.

The sentence uses стюардесса because the speaker is referring to a woman.

Спокойно means calmly.

It modifies the verb попросила:

• стюардесса спокойно попросила = the flight attendant calmly asked

So it describes the manner in which she spoke.

It does not mean that she asked them to stay calm. If Russian wanted to say that, it would need a different structure, for example something involving сохранять спокойствие or успокоиться, depending on the meaning.

Нас is the accusative form of мы (we/us).

The verb попросить often works like this:

• попросить + кого + infinitive
• to ask someone to do something

So:

• попросила нас не вставать
• literally: asked us not to stand up

More examples:

• Он попросил меня подождать. = He asked me to wait.
• Я попросил их помочь. = I asked them to help.

So нас is there because we are the people being asked.

The dictionary pair is:

• просить = imperfective
• попросить = perfective

Here, попросила is perfective because it refers to one completed act of asking. The flight attendant made the request once, as a complete event.

Compare:

• Она просила нас не шуметь. = She was asking / used to ask us not to make noise.
  This can sound repeated, ongoing, or less focused on completion.
• Она попросила нас не шуметь. = She asked us not to make noise.
  This is a single completed request.

In your sentence, one completed request fits perfectly.

This is about verbal aspect.

• вставать = imperfective = to stand up / get up
• встать = perfective = to stand up once, to get to one’s feet

After попросила, Russian often uses the infinitive that best matches the intended nuance.

Here не вставать is natural because it means not to be getting up / not to stand up as a general instruction during that period. It sounds like a standard prohibition or rule.

• попросила нас не вставать = asked us not to stand up

Using не встать here would sound much less natural.

A useful rule of thumb:

• in prohibitions and instructions, Russian very often prefers the imperfective:
  не курить, не входить, не открывать, не вставать

Yes, Russian can use чтобы, but the infinitive version is simpler and more standard here.

Compare:

• стюардесса попросила нас не вставать = the flight attendant asked us not to stand up
• стюардесса попросила, чтобы мы не вставали = the flight attendant asked that we not stand up

Both are grammatical. The first one is more compact and very natural.

The чтобы version is often used when:

• the sentence would be awkward with an infinitive
• the subject of the second action needs to be very explicit
• the speaker wants a slightly fuller clause

But here, попросила нас не вставать is the most straightforward choice.

Yes, Russian word order is flexible, but this order is the most neutral and natural.

• стюардесса спокойно попросила нас не вставать

This follows a common pattern:

• verb of request + person asked + infinitive

You could move things around for emphasis:

• Стюардесса попросила нас спокойно не вставать — this sounds odd, because спокойно now seems to attach to не вставать
• Нас стюардесса спокойно попросила не вставать — possible, but more marked, with emphasis on нас
• Стюардесса нас спокойно попросила не вставать — possible in speech, but less neutral

So the original word order is a good standard model to learn from.

In this airplane context, to stand up is the best translation.

• вставать can mean to get up in some situations, especially from bed or from sitting
• but on a plane, when the flight attendant tells passengers не вставать, it means don’t stand up

So:

• стюардесса спокойно попросила нас не вставать
• the flight attendant calmly asked us not to stand up

The main stresses are:

• турбуле́нтность
• длила́сь
• недо́лго
• стюарде́сса
• споко́йно
• попроси́ла
• не встава́ть

Stress is important in Russian because it is not always predictable. These are worth learning as whole-word pronunciations.

Yes, it is natural and correct.

A slightly more modern or official alternative would be:

• Турбулентность длилась недолго, и бортпроводница спокойно попросила нас не вставать.

That said, your original sentence sounds completely normal. The main difference is vocabulary choice:

• стюардесса = common everyday word
• бортпроводница = more official/professional term

So as a learner, you can treat the sentence as a good natural example of real Russian.