Plane passenger baffled by 'stream' outside window mid-flight they've never seen before despite being on 100s of trips

A frequent flyer who has been on ‘hundreds of flights’ was left baffled after spotting ‘stream’ outside the plane window mid-flight.

The passenger was on board a plane when they saw what looked like stream of air rolling over the wing. 

Despite taking ‘hundreds’ of flights, the passenger said they had ‘never noticed’ it before. 

So, in an attempt to determine what it actually was, they turned to Reddit.

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What was the stream outside the plane window?

When it comes to flying, there are all sorts of questions passengers might have, like why do we use the brace position? And what causes the weird sinking feeling after take-off?

Now, one seasoned airplane passenger has been left baffled after seeing what looked like a stream of steam or air passing over the wing while looking out the plane window. 

“What causes this stream?” they asked alongside a clip. 

“Been on 100s of flights and never noticed this. What causes this? What conditions have to be met? Thank you.”

And it didn’t take long until they got their answer. 

According to a fellow Reddit user, the footage shows a ‘beautifully visible vortex’. 

The person went on to explain that the vortex is a spinning cylinder of air that is created by the small triangular shape on the engine cowling, and is there to help keep flow over that part of the wing. 

“The air flowing around the engine cowling gets disturbed, so when it reaches the wing, it’ll have much less energy than air flowing over other parts of the wing,” they explained. 

“This can cause that part of the wing to stall.

“That vortex helps re-energise the flow that was disturbed by the engine cowling and also acts like a little wall, ensuring that any flow separation that does still happen on the part of the wing affected by disturbance from the engine cowling doesn’t spread to other parts of the wing.”

So there you go.

Why was it so visible on this particular flight?

The person who shared the detailed explanation also revealed why the passenger saw it on that occasion despite not seeing the occurrence on any previous flights. 

They said that the core of the vortex is at much lower pressure than the surrounding air, and under certain conditions, this causes the moisture in the air to condense and effectively become a little cloud.

Which is exactly what you’re seeing in the clip. 

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