Надеюсь, мы долетим до Москвы вовремя.

No. The sentence has two different subjects:

• (Я) надеюсь = I hope
• мы долетим = we will make it / fly there

So надеюсь is singular because the speaker is saying I hope, while мы belongs to the second part: we will arrive.

The full structure is essentially:

(Я) надеюсь, (что) мы долетим до Москвы вовремя.

Russian often omits subject pronouns when the verb ending already makes the subject clear.

• надеюсь already means I hope
• the ending -юсь shows 1st person singular

So Надеюсь by itself is very natural. You can say Я надеюсь, but that adds a little more emphasis or explicitness.

Надеюсь is the 1st person singular present tense of надеяться.

So:

• я надеюсь = I hope
• dictionary form: надеяться

The verb is reflexive, which is why it ends in -ся / -сь. In this form, after a vowel, it appears as -сь: надею-сь.

Because Надеюсь introduces another clause:

• Надеюсь, мы долетим до Москвы вовремя.

This is basically a shortened version of:

• Надеюсь, что мы долетим до Москвы вовремя.

Even when что is omitted, the comma usually stays.

Yes, absolutely.

Both are natural:

• Надеюсь, мы долетим до Москвы вовремя.
• Надеюсь, что мы долетим до Москвы вовремя.

Russian often leaves out что after verbs like I hope, I think, I know, especially in everyday speech. The version without что can sound a bit lighter or more conversational.

Because долетим comes from a perfective verb: долететь.

In Russian, perfective verbs do not have a true present tense. Their “present-looking” forms actually refer to the future.

So:

• долетим = we will make it / we will fly as far as
• not we are making it

This is a very important Russian pattern.

The prefix до- adds the idea of reaching a point or going all the way to something.

So:

• лететь = to fly
• долететь = to fly all the way to / to make it as far as / to reach by flying

In this sentence, долетим до Москвы means not just fly, but successfully get to Moscow by plane.

Because долететь normally goes with до + genitive.

• долететь до Москвы = to make it as far as Moscow / reach Moscow by flying

If you use a different verb, you may get a different preposition:

• прилететь в Москву = to arrive in Moscow by plane

Both are possible ideas, but the given sentence specifically uses долететь, which naturally combines with до.

Because the preposition до requires the genitive case.

• nominative: Москва
• genitive: Москвы

So:

• до Москвы = to/up to Moscow

For many feminine nouns ending in -а, the genitive singular changes -а to -ы or -и.

Вовремя means on time or in time, depending on context.

In this sentence, it most naturally means:

• on time
• without being late

So the idea is that they hope to reach Moscow at the expected or necessary time.

Because вовремя is an adverb meaning on time / in time.

This is different from во время written as two words, which usually means during and is followed by a noun:

• вовремя = on time
• во время полёта = during the flight

So in your sentence, вовремя must be one word.

Yes. Russian word order is fairly flexible.

For example, you could also hear:

• Мы долетим до Москвы вовремя, надеюсь.
• Надеюсь, вовремя долетим до Москвы.

But the original:

• Надеюсь, мы долетим до Москвы вовремя.

is a very natural, neutral way to say it. It starts with the speaker’s attitude (I hope) and then gives the main event.