kekkou de haraimodosi wo onegaisuru.

It is read けっこう.

That can confuse learners because 結構 is also read けっこう, but it is a completely different word. Here, 欠航 means a cancellation of a flight or other service.

• 欠 = lack / missing
• 航 = voyage / flight / navigation

So 欠航 is specifically the cancellation of a flight, ferry, etc.

In this sentence, 欠航 is a noun.

Japanese often uses nouns where English might use a clause like the flight was canceled or because the flight was canceled.

So instead of a full verb sentence, Japanese can say:

• 欠航で = because of the cancellation / due to the flight cancellation

You can think of it as a compact, noun-based expression.

Here, で shows reason/cause.

So:

• 欠航で = because of the cancellation
• due to the flight being canceled

This is a common use of で after a noun that describes a situation or cause.

Compare:

• 病気で休む = be absent because of illness
• 事故で遅れる = be late because of an accident
• 欠航で払い戻しをお願いする = request a refund because of the cancellation

So で is not marking location here; it is marking the reason.

Because 払い戻し is the thing being requested.

• 払い戻し = refund
• を = marks the direct object
• お願いする = to request

So 払い戻しをお願いする means to request a refund.

Even though お願いする is a little broader than a simple verb like ask, the structure still works like:

• X をお願いする = request X

Here, お願いする means to request or to ask for in a polite, service-oriented way.

It comes from お願い:

• 願う = to wish / request
• お願いする = to make a request

In practical use, お願いする often sounds softer and more polite than a very direct demand.

For example:

• 確認をお願いする = request confirmation
• 対応をお願いする = request assistance / handling
• 払い戻しをお願いする = request a refund

So yes, it is similar to to ask, but in Japanese it has a polite, formal-service flavor.

Because this looks like a dictionary-style phrasebook expression rather than the exact sentence you would most naturally say out loud.

The dictionary form お願いする often appears in:

• phrasebooks
• vocabulary lists
• textbook example headings
• descriptions of actions

In actual conversation, you would usually say:

• 欠航で、払い戻しをお願いします。
• 欠航なので、払い戻しをお願いします。

So the given sentence is best understood as something like:

• Request a refund due to the cancellation.

It describes the action, rather than giving the most natural spoken line.

Yes. Japanese often leaves out information that is obvious from context.

Possible omitted information includes:

• the flight or ticket
• I as the person making the request
• my ticket/fare as what should be refunded

A fuller version might be:

• 欠航なので、払い戻しをお願いします。
• 欠航になったので、航空券の払い戻しをお願いします。

So the original sentence is short and compressed, but very normal for study materials or phrasebook-style Japanese.

Not very often in normal conversation.

It sounds a bit like a label, memo, or phrasebook entry. A native speaker would more naturally say something like:

• 欠航なので、払い戻しをお願いします。
• 便が欠航になったので、払い戻しをお願いします。
• 欠航ですので、払い戻しをお願いできますか。

Why?

Because spoken Japanese usually needs:

• a more conversational reason marker such as ので
• a polite sentence ending like お願いします or お願いできますか

So the original is understandable, but it is slightly compressed.

Both can express the reason, but 欠航なので sounds more natural and complete in everyday conversation.

• 欠航で = due to the cancellation
• 欠航なので = because it was canceled / because there is a cancellation

Nuance:

• 欠航で is compact and somewhat matter-of-fact
• 欠航なので feels more like a full spoken explanation

So:

• 欠航で払い戻しをお願いする = compact, phrasebook-like
• 欠航なので、払い戻しをお願いします = more natural spoken Japanese

They are similar, but not always identical in usage.

• 払い戻し is very common for tickets, fares, reservations, admissions, and transportation-related refunds
• 返金 is a more general word for refunding money

In a travel situation, 払い戻し is especially natural.

Examples:

• 切符の払い戻し = ticket refund
• 航空券の払い戻し = airline ticket refund
• 返金してください = please refund the money

So in this sentence, 払い戻し is a very appropriate choice.

Not only airplanes, but it is especially common for flights and sometimes ships or ferries.

For trains, Japanese more often uses:

• 運休 = service suspension / canceled service

So:

• 飛行機が欠航 = the flight is canceled
• 電車が運休 = the train service is suspended

That is why 欠航 fits very naturally in an airport or airline context.