Hann spurði hvort við ættum að aflýsa ferðinni, en hún leit á himininn og sagði að skýlaust kvöld eins og þetta kæmi ekki oft.

Hvort introduces an indirect yes/no question, so here it means whether:

Hann spurði hvort við ættum að aflýsa ferðinni
= He asked whether we should cancel the trip

A learner may expect ef, because ef can sometimes mean whether in less formal usage, but hvort is the standard and clearest choice after a verb like spurði when the question is yes/no.

Ættum is the 1st person plural form used in the expression eiga að, which often means should, ought to, or be supposed to.

So:

við ættum að aflýsa
= we should cancel

Even though this form is historically a past-subjunctive form, in modern Icelandic it very often works like a softened suggestion, recommendation, or conditional-like should, not a true past tense.

That að is the infinitive marker, so it works like English to:

að aflýsa = to cancel

So:

við ættum að aflýsa ferðinni
literally: we should to-cancel the trip
natural English: we should cancel the trip

Because aflýsa takes a dative object in Icelandic.

The base noun is ferð = trip / journey.
Here it appears as ferðinni, which is dative singular definite: the trip.

So this is a good example of something English speakers often have to learn: Icelandic verbs often require a specific case, and it is not always the accusative.

• ferð = a trip
• ferðin = the trip
• ferðinni = to/for the trip, or after a dative-taking verb like aflýsa

There are two reasons:

1. Definiteness: it refers to a specific trip, so Icelandic uses the suffixed definite article: ferðin / ferðinni = the trip
2. Case: because aflýsa takes the dative, you get ferðinni, not nominative ferðin or accusative ferðina

So the form is determined by both meaning and grammar.

Leit is the past tense of líta, meaning look.
The expression líta á means look at.

So:

hún leit á himininn
= she looked at the sky

The noun himininn is in the accusative singular definite, because líta á takes an accusative object.

This is different from English, where the object form usually does not visibly change.

They are doing two different jobs:

1. að aflýsa: here að is the infinitive marker = to
2. sagði að: here að is a conjunction = that

So in the same sentence you get:

• að aflýsa = to cancel
• sagði að ... = said that ...

This is very common in Icelandic and can be confusing at first, but the role is usually clear from the structure around it.

Skýlaust comes from:

• ský = cloud
• -laus = without / -less

So skýlaus means cloudless.

It becomes skýlaust here because it agrees with kvöld, and kvöld is:

• neuter
• singular
• indefinite

A neuter singular adjective often takes the ending -t, so:

skýlaust kvöld = a cloudless evening

Here þetta means this, referring back to an understood kvöld:

skýlaust kvöld eins og þetta
= a cloudless evening like this [one]

You can think of it as short for:

eins og þetta kvöld

The form þetta is neuter singular nominative/accusative, matching kvöld.
Þessu would be dative, which does not fit here.

So eins og þetta is essentially like this one / like this.

Kæmi is the past subjunctive of koma (to come).

This is one of the trickier parts for English speakers, because it does not simply mean past time here. In a clause after a past reporting verb like sagði, Icelandic often uses the subjunctive to present what someone said, thought, believed, or judged.

So:

sagði að ... kæmi ekki oft
is a natural reported-speech style meaning something like
said that ... doesn’t come often

Using kemur would sound more like a plain direct factual statement inside the clause.
Using kæmi gives it the flavor of reported viewpoint/judgment.

Not necessarily. Even though kæmi can look like a conditional or past form to an English speaker, here it is better understood through Icelandic grammar, not word-for-word English tense matching.

In this sentence, kæmi ekki oft expresses a general idea within reported speech:

a cloudless evening like this doesn’t happen often

So the form is more about subjunctive mood in reported speech than about literal past time or a real English would.

Yes. Ekki oft is the normal way to say not often.

So:

kæmi ekki oft
= doesn’t come often / doesn’t happen often

The order is very natural in Icelandic:

• finite verb: kæmi
• negation: ekki
• adverb of frequency: oft

That part matches English quite closely: not often.