A bright sphere hanging motionless in the sky? Party and weather balloons mistaken for UFOs

5 min read

A silvery, glinting sphere has stood in the same spot in the sky for days, a white dot keeps shining after dusk, a metallic object drifts slowly in front of the clouds. Behind these there is often a balloon: an escaped helium balloon, a weather balloon or an advertising balloon. Balloons also played leading roles in the biggest mistakes in UFO history, from Roswell to the Pentagon's recent UFO videos. We show you how to recognize them.

What kinds of balloons fly in the sky?

Party balloons. Helium-filled latex balloons expand after they rise and burst. Silvery foil balloons (mylar), however, do not expand, and they can drift in the wind for days, even weeks, often several kilometers high. On holidays and at events, dozens may be released at once.
Weather balloons. Meteorological services around the world launch radiosondes every day: a latex balloon filled with helium or hydrogen that carries a small measuring instrument aloft. In Hungary, HungaroMet carries out such measurements in Pestszentlőrinc, Budapest. At launch the balloon is about 1.5 meters across; as it rises it expands more and more, and at an altitude of about 30 kilometers, inflated to about 10 meters, it bursts. The measuring instrument descends back to the ground by parachute.
Hobby and research balloons. Amateur radio operators and students also launch small balloons, which can circle the Earth for months and report their position by radio.
Advertising and lighting balloons. Large, helium-filled, often oval or spherical balloons used at events, construction sites and film shoots, often lit from the inside. Sometimes they break loose.

The launch and burst of a weather balloon and the descent of the measuring instrument. Sky Glitch chart

What does it look like?

By day: a bright, white or silvery dot that glints in the sunlight and barely moves. Through a telescope or at high magnification it may look like a sphere, a teardrop, a "disk" or a "cylinder."
At dusk: a bright "star" that is not a star. A balloon flying high is still lit by sunlight even after the Sun has already set down below. By our own calculation, a balloon 30 kilometers high directly overhead is still reached by sunlight when the Sun is 5.5 degrees below the horizon.
Slow, steady drift with the wind, or hovering almost motionless. No sound.
Sometimes it rotates, wobbles, flickers. A foil balloon turning in the sunlight occasionally flashes, as if it were signaling.
It suddenly disappears. If it bursts, or if it enters a cloud, it vanishes from one moment to the next.

Why is it misleading?

We don't know how far away it is. A 40-centimeter balloon drifting a few hundred meters away and a large object kilometers away appear as the same-sized dot. The impression of a large, distant object immediately turns it into a "huge" and "fast" UFO.
Motion is deceptive. If the observer is moving (in a car, in an airplane, or with a camera on a drone), even a stationary or slowly drifting balloon can appear to be racing or "maneuvering." This effect is called parallax.
The wind direction aloft is different. A balloon high up can drift in a completely different direction from the way the wind is blowing down below. That is why it can seem to be moving "against the wind."
Metallic sheen. A foil balloon gleams metallically in the sunlight, as if it were a solid, machine-like object.

Real cases

Roswell, 1947. Even the world's most famous UFO case began with the remains of a balloon train: the debris came from one of the balloon trains of a secret American program called Mogul, which attempted to detect the sound waves of Soviet nuclear tests.
Saint-Zacharie, France, 2015. A man saw a car-sized, oval object bearing a logo glide silently between mobile homes. The French GEIPAN itself considered an advertising balloon the most likely explanation.
Gulf of Mexico, 2023. An American fighter pilot saw a slow-moving object on his infrared camera that was hot on the bottom and cold on top, which he said resembled an Apollo space capsule. The U.S. government's UFO investigation office, AARO, concluded with moderate confidence in 2024 that he had seen a commercial lighting balloon: the upper half of these balloons is black and reflective, the lower half white, which produces exactly this kind of thermal image.
Syria, 2022. In 2023 the Pentagon released a video recorded by an MQ-9 drone of a metallic sphere that moved fast in the footage. According to Bellingcat's investigators, the object was at most about 43 centimeters wide, and its motion was caused by the drone's own movement. The simplest explanation is a party balloon, especially since the footage was recorded during a holiday.
Yukon, Canada, 2023. On February 11, 2023, an American F-22 fighter jet shot down an unidentified object over Canada. On that day, an Illinois amateur radio club lost contact with its 80-centimeter foil balloon, which had been circling for months carrying a payload of about 16 grams and happened to be passing through the area. The connection was not officially confirmed, and the remains of the downed object were not found.

How can you check?

Watch it for longer. A balloon barely moves over minutes or even hours, or drifts slowly and steadily.
Check the wind direction aloft. Weather websites and meteorological services also publish upper-level wind direction data. If the object is moving in the same direction, a balloon is likely.
Use binoculars or a telescope. Often you can make out the spherical shape, the shiny foil, or the small sonde hanging below the balloon.
Think about when you saw it. If it shone high up in one spot after dusk and its light slowly faded, it may have been a high-flying balloon still in sunlight.
Look for an event. Wedding, birthday, grand opening, graduation: balloons are often released on such occasions.
If you find a balloon, for example a radiosonde that has come down, the label on it tells you whose it is and where it can be sent back.

Quick identifying signs

Bright, white or silvery sphere, even in daytime
Almost motionless or drifting slowly
Complete silence
Can shine even after dusk if it is high up
May flash occasionally as it rotates

Did you see something strange in the sky? Start with our decision tree, and if you can't find the answer, send us the footage!