Cuando empezamos a aterrizar, vi la pista y los edificios desde arriba.

Empezamos is in the preterite, which is used for a completed action or for the moment something begins. Here, the sentence refers to the point when we started to land.

If you said cuando empezábamos a aterrizar, that would sound more like when we were starting to land, focusing on the action as ongoing or in progress. That is possible in some contexts, but empezamos is the more natural choice here if the speaker is referring to a clear moment in the sequence of events.

Empezar a + infinitive means to begin/start to do something.

So:

• empezamos a aterrizar = we started to land

This structure is very common in Spanish:

• empezar a hablar = to start speaking
• empezar a llover = to start raining
• empezar a trabajar = to start working

The a is required with empezar before another verb.

Vi is the preterite form of ver for yo:

• yo vi = I saw

It is irregular in the sense that it does not take an accent, and its preterite forms are:

• vi
• viste
• vio
• vimos
• visteis
• vieron

Veía is the imperfect form, meaning I was seeing / I used to see / I could see, depending on context. In this sentence, vi is used because the speaker is describing a completed event in the past: at that point, they saw the runway and the buildings.

Because the sentence is narrating past events.

• empezamos a aterrizar = one past action
• vi la pista y los edificios = another past action

This is a very common storytelling pattern in Spanish: one event happens, and then another event happens in that situation.

The sentence means that when the landing began, I saw the runway and the buildings from above.

Spanish often uses the definite article (el, la, los, las) in places where English might or might not use the.

Here:

• la pista = the runway
• los edificios = the buildings

These are specific things the speaker could see. In context, they are understood as the runway and the buildings at the airport or below the plane, so the article sounds natural.

In this sentence, la pista means the runway.

But pista can mean different things depending on context, for example:

• runway at an airport
• track for running or racing
• clue in a mystery or game
• dance floor in some expressions

So pista does not always mean runway. Context tells you which meaning is intended.

Desde arriba means from above or from up high.

• arriba on its own usually means up, upstairs, or above
• desde arriba specifically expresses the point of view: from above

In this sentence, the speaker is saying they saw the runway and buildings from above, which fits the context of being on a plane.

Yes, desde lo alto is possible, but it sounds a bit more literary or descriptive.

• desde arriba = from above, from up there
• desde lo alto = from on high / from a height

In everyday speech, desde arriba is simpler and more common.

In normal understanding, desde arriba describes the viewpoint of seeing:

• I saw the runway and the buildings from above

So it mainly goes with vi.

Spanish often places adverbial phrases like this at the end of the sentence. That is a very natural position.

If needed, the speaker could also say:

• Desde arriba, vi la pista y los edificios.

That gives a bit more emphasis to the viewpoint.

Here it is followed by the indicative: cuando empezamos.

That is because the speaker is talking about a real event in the past.

With cuando, Spanish uses:

• indicative for habitual, present, or past facts/events
• subjunctive for future or not-yet-realised events in certain contexts

Compare:

• Cuando empezamos a aterrizar, vi la pista.
  = real past event → indicative

• Cuando empecemos a aterrizar, mira por la ventana.
  = future event → subjunctive

Yes. Literally, aterrizar means to land, especially for planes. But it can also be used more broadly, sometimes even figuratively.

For example:

• El avión aterrizó. = The plane landed.
• Aterrizamos en Madrid a las ocho. = We landed in Madrid at eight.
• Figuratively, aterrizar en la realidad can mean something like to come back down to earth.

In this sentence, though, it clearly refers to an airplane landing.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

• empezamos already tells you it means we started
• vi already tells you it means I saw

So:

• Cuando empezamos a aterrizar, vi...

is perfectly natural without nosotros or yo.

You could include them for emphasis:

• Cuando nosotros empezamos a aterrizar, yo vi...

But that would usually sound unnecessary unless you want contrast or emphasis.

A Spain pronunciation, roughly broken down, is:

Cuando → KWAN-doh
empezamos → em-peh-THA-mos (in much of Spain, z sounds like th in think)
a aterrizar → a a-te-rri-THAR
vi → bee
la pista → la PEES-ta
y los edificios → ee los eh-dee-FEE-thyos
desde arriba → DEZ-de a-RREE-ba

A more connected pronunciation would sound something like:

KWAN-doh em-peh-THA-mos a a-te-rri-THAR, bee la PEES-ta ee los eh-dee-FEE-thyos DEZ-de a-RREE-ba.

Yes, in context that can work as a natural English translation. But grammatically, vi is simply I saw, not specifically I could see.

Sometimes English uses could see where Spanish just uses ver in the preterite or imperfect, depending on the situation. So I saw the runway and the buildings from above is the more direct match, while I could see... may be a smoother translation in some contexts.