This is the escape route they prepared for themselves.

It is not advisable to burn your boats because the gap between the two sides is too big in terms of strength and information.

The chances of winning are not great, and burning your boats is tantamount to semi-suicide, which is meaningless. Modern warfare cannot be resolved by morale alone.

"Okay." Xu Xin nodded. "Always be prepared. They may not be able to hold out for long."

"I'll send you to the underworld."

Soon, several people came to the underground world through the root elevator of the World Tree.

The underground world here is under the entire deep sea.

Moreover, because there are no crystal veins here, the underground world is pitch black.

When Xu Xin and his companions walked out of the World Tree's root elevator, they were completely pitch dark all around.

He immediately took out a tree house core and illuminated the surroundings.

But the range that can be illuminated is only a few dozen meters around.

There was no soil on the rocky ground, and the surroundings were extremely quiet, like a dark abyss, so quiet that it was frightening.

This was completely different from the underground world he had seen before, where monsters and terrifying beasts were everywhere.

This is an unexplored dark world.

"After all, this place is relatively close to the alien invaders' base, only a little over a thousand kilometers away. They haven't conducted any experiments on behemoths here," the man explained again to Xu Xin and the others. "Also, there aren't any crystal mines nearby, so except for the area very close to their base, the rest of the area is largely undeveloped."

Before the man finished speaking, suddenly, two columns of strong light shot out from a distance of about 200 meters away from the few people, illuminating the surrounding area.

Xu Xin and Xu Ying also saw the source of the strong light.

It was the flying shuttle the man had mentioned.

"Is this the aircraft you were talking about? It's so small..." Xu Ying complained while standing next to the flying shuttle.

This is a very small aircraft with three propellers on the left and right rear.

The interior space is very small. Excluding the driving position, only four or five people can sit in the back.

It’s about the same size as the interior of a car or a small helicopter.

However, the propellers are very large, and each one is longer than the cabin.

It looks like a large remote-controlled drone.

"This is our flying shuttle, a version suitable for the underground world." The man walked over to the shuttle. "It's not very fast, but it's very flexible and suitable for traveling through the complex terrain of some areas in the underground world."

As he spoke, the man opened the hatch and entered the cockpit: "You don't know how to drive, I will take you there."

Xu Xin and Xu Ying looked at each other, and then entered.

The interior space is really small. You can only sit in it like you would in a car and cannot stand up.

"Close the hatch, we're about to take off."

The propeller spun rapidly, carrying the entire fuselage into the air.

But what is surprising is that even though there are three large propellers spinning at such a speed, there is basically no sound.

Silent propeller?

"The sound is so quiet." Xu Xin exclaimed.

This technology is really confusing. The noise is probably not even as loud as a computer fan...

"Of course it has to be small. This flying shuttle is used to explore the underground world. If the noise is too loud, it will mask some key sounds and attract large numbers of giant beasts. Therefore, it must be secretive."

That’s not bad, at least we won’t be discovered by alien invaders because of the sound.

The sense of security is greatly enhanced.

The shuttle took off into the air, rising to a height of nearly a hundred meters above the ground.

"Hold on tight."

This area was relatively flat, so the flying shuttle immediately began to accelerate laterally.

After the strong push back feeling, the speed began to stabilize.

At the same time, a headlight turned on from under the shuttle, illuminating a large circular area of ​​several hundred meters below.

"Wow... this thing is really good."

Xu Xin looked out the window.

The underground world is not as flat as the human base in the underground world. After all, it was specially selected. It can even be said that most of the terrain in the underground world is very rugged.

The terrain here includes both up and down.

The ground and the dome are sometimes even connected together in large areas, like a huge cave.

Therefore, if you want to travel through the underground world, first of all, ground tools are impossible.

Among flying vehicles, ordinary airplanes, which are fast but not flexible, are absolutely unable to travel long distances.

The extremely flexible flying shuttle, which can even hover, is the most suitable means of transportation for traveling in the underground world.

But the flying shuttle has a disadvantage, which is that its speed is not very fast, at most only about 500 to 600 kilometers.

This speed is far from that of civil airliners thousands of years ago.

Fortunately, they were only a thousand kilometers away from their destination, and a speed of five or six hundred kilometers per hour was enough.

Fortunately, the location is relatively close. Using this kind of shuttle to cross the ocean would be too slow. Especially since the size of the Earth is no longer comparable to what it was before.

"Are you wondering how we can explore this underground world when this shuttle is so slow?" the man who was driving the shuttle turned around and asked.

"Hey, can you look ahead? Are you not concentrating on flying the plane? Aren't you afraid of a collision?" Xu Ying complained.

Five hundred kilometers per hour is already a very fast speed for humans.

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