unkousaikai ga asita ni naru tame, syukuhakuentyouse zaru wo enai.

Literally, it means something like the resumption of operations becomes tomorrow.

In natural English, that usually comes out as:

• Operations will resume tomorrow
• The resumption of service has been pushed back to tomorrow
• Service will not restart until tomorrow

The key point is that 明日になる with なる does not mean turn into tomorrow in a strange literal sense. It means that the scheduled time or resulting state is tomorrow.

Here, が marks 運航再開 as the subject of なる.

So the structure is:

• 運航再開 = resumption of operations / service
• が = subject marker
• 明日になる = becomes tomorrow / is set for tomorrow

So the meaning is: the resumption of operations will be tomorrow.

You could sometimes see は instead, but が is very natural here because it simply identifies what is becoming 明日.

With なる, に marks the result or new state.

So:

• 明日になる = become tomorrow / end up being tomorrow
• 来週になる = be next week
• 延期になる = be postponed

Even though 明日 is a time word, に is used because it is the endpoint or result of the change.

ため means because, since, or due to in this sentence.

So:

• 運航再開が明日になるため = because operations will resume tomorrow

This ため is fairly formal and written-sounding. It is more objective and less conversational than から or ので.

A more casual version might be:

• 運航再開が明日になるので、...

せざるを得ない means have no choice but to do or cannot avoid doing.

It is a formal grammar pattern:

• V-ざるを得ない = cannot help but do V
• must do V because the situation leaves no alternative

So in this sentence, it means:

• have no choice but to extend the stay

This expression often carries a nuance of reluctance. It suggests that the speaker does not really want to do it, but circumstances make it necessary.

Because する is irregular, and this pattern uses an older grammatical form.

In ざるを得ない, the ざる attaches to the old negative base of the verb. For する, that base is せ.

So:

• する → せざるを得ない
• 行く → 行かざるを得ない
• 食べる → 食べざるを得ない

This is why せざるを得ない is correct, not しざるを得ない.

You also see the same old form in expressions like:

• せずに = without doing

It is understandable, but it sounds compressed.

A more fully spelled-out version would usually be:

• 宿泊を延長せざるを得ない = have no choice but to extend the stay
• possibly 宿泊延長をせざるを得ない, though this is less natural than 宿泊を延長する

So the given sentence feels a bit like a notice, memo, or very compact written style, where words get packed together.

In ordinary Japanese, 宿泊を延長せざるを得ない would be the more natural phrasing.

This is related to the compressed style of the sentence.

If you expand it into more standard Japanese, you would normally expect:

• 宿泊を延長せざるを得ない

Here:

• 宿泊 = lodging / stay
• を = object marker
• 延長する = extend

In the original sentence, 宿泊延長 is treated almost like a compact noun phrase, and the sentence drops some of the fuller structure. That kind of shortening happens in formal notices and headline-like writing.

It is not stated explicitly.

Japanese often omits the subject when it is clear from context. Depending on the situation, it could mean:

• I have no choice but to extend my stay
• We have no choice but to extend our stay
• Passengers/guests have no choice but to extend their stay

The exact subject has to be inferred from the context.

Yes, it is fairly formal and written in a stiff, concise style.

The formal feeling comes from things like:

• ため instead of ので or から
• ざるを得ない instead of a more everyday expression
• the compressed wording 宿泊延長

A more conversational version might be:

• 運航再開が明日になるので、宿泊を延長しないといけない。
• 運航再開が明日になるので、もう一泊するしかない。

Those sound more natural in everyday speech.

ざるを得ない often emphasizes that the situation leaves no alternative.

Compare:

• 延長しなければならない = must extend
• 延長せざるを得ない = have no choice but to extend

The second one sounds more like:

• the speaker is being forced by circumstances
• the decision is reluctant or unavoidable
• there is no realistic way around it

So in this sentence, it suggests: because service will not resume until tomorrow, extending the stay is unavoidable.