In which clouds do they usually form?

Mid-level layers like altocumulus

What often triggers the freezing?

Aircraft passing through the cloud

What happens once ice crystals form?

They grow by taking water from droplets

Fallstreak Hole Quiz: Hole-Punch Clouds Explained

This fallstreak hole quiz looks up at a perfect circle punched through a sheet of cloud. Play 10 interactive questions on supercooled water droplets below freezing, aircraft that trigger sudden freezing, ice crystals that grow at the droplets' expense, streaks of falling ice in the middle, a 2010 study, UFO rumors and why the holes can grow for kilometers.

Start Fallstreak Hole Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Name
What is another name for a fallstreak hole?
Cloud
In which clouds do they usually form?
Supercooled
What are supercooled droplets?
Trigger
What often triggers the freezing?
Growth
What happens once ice crystals form?
Fall
What hangs in the middle of the hole?
Study
What did a 2010 study link fallstreak holes to?
UFO
Why are they sometimes reported as UFOs?
Size
How large can a fallstreak hole grow?
Snow
What can these events add near airports?

Explanations: answer key for all 10 questions

Q1: What is another name for a fallstreak hole?
Answer: Hole-punch cloud
It looks punched out.
Q2: In which clouds do they usually form?
Answer: Mid-level layers like altocumulus
Thin layered clouds work best.
Q3: What are supercooled droplets?
Answer: Liquid water below 0 C
They need a trigger to freeze.
Q4: What often triggers the freezing?
Answer: Aircraft passing through the cloud
Air cools behind wings and propellers.
Q5: What happens once ice crystals form?
Answer: They grow by taking water from droplets
Droplets evaporate around them.
Q6: What hangs in the middle of the hole?
Answer: Streaks of falling ice
They are a kind of virga.
Q7: What did a 2010 study link fallstreak holes to?
Answer: Aircraft flying through clouds
Scientists studied flight paths.
Q8: Why are they sometimes reported as UFOs?
Answer: Their strange round shape
They look unusual.
Q9: How large can a fallstreak hole grow?
Answer: Kilometers across
It spreads as ice forms.
Q10: What can these events add near airports?
Answer: Extra snow or rain
Planes can boost precipitation.

When Planes Punch Holes in Clouds

A fallstreak hole, or hole-punch cloud, is a round or long gap in a layer of mid-level cloud, such as altocumulus. These clouds can contain supercooled droplets, liquid water below 0 C that has not frozen because it needs a trigger.

When an aircraft passes through, air cools as it expands behind wings and propellers, causing some droplets to freeze. Ice crystals then grow by taking water from surrounding droplets, which evaporate, opening a hole. Streaks of falling ice, a kind of virga, hang in the middle, and the hole can grow kilometers across.

A 2010 study linked these holes to aircraft flight paths, and planes passing through such clouds can even add extra snow or rain near airports. Their strange round shapes sometimes lead to UFO reports, but the science is all about ice and water.

What This Quiz Teaches

Weather fans will enjoy these questions.

What fallstreak holes are
What supercooled droplets are
How aircraft trigger them
What falls from them
Why they look strange

Did You Know?

They often appear near airports.
Long canal-shaped versions also form.
Photos go viral after big ones.
They last for an hour or so.
Old reports predate aviation.