The UFO of Saint-Didier (1978)


A soldier saw three very luminous objects fly while changing their relative position several times. Upon losing them out of sight, he went into another room and then into the plane parking lot alongside colleagues. There, the men observed an orange-yellow object with the same brightness. It apparently departed in a well-defined direction while zigzagging, accelerating and stopping its motion suddenly.

A possible explanation would be the combination of a sighting of three planes engaged in a military exercise followed by the sighting of the moon.

The data don’t seem to be sufficient to validate or invalidate that hypothesis.



France has an official group devoted to the study of UFO/UAP called the GEIPAN. It aims at critically and objectively assessing UAP reports.
It divides them into four groups:

  • A: a mundane cause has been positively identified.
  • B: a mundane cause has been plausibly identified.
  • C: there is not enough data to draw any conclusion as to the origin of the phenomenon.
  • D: the data at our disposal suffice for ruling out all conventional explanations as unlikely.

My purpose here is to systematically review all UAP of the class „D“ and try (with my modest means) to evaluate whether or not the classification was justified.

It is worth noting that the GEIPAN itself became more mature over the years so that they recently reclassified several „D“ cases, especially with respect to the misidentification of planets and stars seen under unusual circumstances.

Description of the case

The incident can be broken down into three phases. It took place in and around military buildings at he airbase of Saint-Didier (in Eastern France).


Air base of Saint-Didier (France)

First phase

On the 20-th of August 1978 at 22:50, a military man saw three strange luminous points in the sky coming from the east.
Their brightness was compared to that of a neon light bulb and their size to that of a ping-pong ball.
The flew in formation while frequently changing their relative position. They formed first a triangle, then flew one behind another before flying one beside another.

He observed them for 10 minutes prior to losing them out of sight.

Second phase

He went into another room with colleagues where they saw an orange-yellow light with the same luminosity at a higher altitude.
They observed it for between 4 to 5 minutes while it stayed immobile.

Third phase

Thereupon they went down to the plane parking lot.

The object was first immobile and then they saw it departing with an erratic motion: it moved along an arc of a circle, accelerated, stopped for 1 or 2 seconds, went a bit backward, and then accelerated again.

Its brightness was continuously diminishing and it finally disappeared.


Unfortunately, the duration of that part of the sighting is not given.
However, since the first witness estimated that its total duration was 15 minutes, we can conservatively estimate that the duration of their stay on the plane parking lot cannot be much longer than 10 minutes.


Plausible explanations

The first soldier thought that the three objects seen during the first phase merged into the orange one observed during the second and third phase. If we accept this, it would seem this was indeed a UFO, as no known object could display all these features.

It is worth noting, however, that it is only an assumption: the first soldier did not see the first three lights morphing into the orange one.

Based on this, we could try to explain the incident through the combination of the sighting of different objects.

At the beginning, the first soldier saw perhaps three planes or helicopters engaged in a military exercise.


Example of planes engaged in a military exercise.

As he walked to the other room upon losing them out of sight, they flew away sufficiently far or perhaps changed their direction so they could no longer be seen from the new point of observation.

Instead, he saw a heavenly body which he found puzzling and misidentified it as being the three lights which merged together. Given the features of that new light (orange-yellow in colour with the size of a ping-pong ball), the moon appears to be a much better candidate than a mere star or planet.


Now, we shall examine the strengths and weaknesses of that explanation.


  • Three days before the sighting, the moon was full.
  • The witnesses did mention seeing stars in the sky but nowhere did they mention seeing the moon as well. This is certainly strange if the object was different from the earth’s satellite.


  • The witnesses describe the object as moving in a well-defined direction before changing its heading. While the auto-kinetic effect (an optical illusion) could account for the chaotic aspect of the object’s motion (accelerating and stopping suddenly), it is more unlikely it could give rise to the illusion of a coherent trajectory. It is doubtful whether the motion of putative thin clouds could have created the illusion that the object moved along an arc of a circle and then erratically accelerated and stopped. This is not impossible but rather unlikely.
  • The soldiers lost the object out of sight after at most 10 minutes at roughly 23:20. Obviously, the moon didn’t disappear that early. So, its seeming disappearance could only have been caused by its being covered by a cloud. The problem is that four of the soldiers clearly stated that it was lost from view because of the distance. One soldier even emphasised that it did not disappear. It is also noteworthy that the sky was described as being cloudless that night in the report. Based on this and other data, there could at most only have been thin clouds. And these might not have been sufficient for completely masking the moon. But even if they did mask it, wouldn’t the soldiers have recognised it again after the wind chased away the putative cloud?
  • If the first objects were indeed planes or helicopters engaged in some military exercise, why didn’t any military person check and find this?
  • Both the three objects and the one that was stationary for several minutes were described as extremely luminous and their brightness was likened to that of a neon-light or a shooting star. It would seem to be a weird coincidence that uncorrelated military planes and a heavenly body would bother appear to soldiers in the same way.
  • Does it often happen that during military exercises, pilots are asked to change their relative position from a triangle to a line and then to another perpendicular line? I might be wrong but this seems to be rather unusual.



This case illustrates the complexity of trying to study UFO reports in a rigorous and objective manner. It does demand a lot of work and the willingness to constantly shove aside one’s pet ideas if they prove to be unsuitable.

I tried to formulate a hypothesis (sightings of two types of uncorrelated objects, namely three military planes and the moon) which would account for all the data at hand.
The strongest argument in its favour consists of the fact that the soldiers failed to mention the presence of the moon even though they mentioned the presence of stars.

The strongest arguments against it are its disappearance before midnight and the strange and unusual character of the military operation that would have involved the first three objects.

Because of these conflicting facts and the dearth of information, I think this incident should be reclassified into the C category („Not enough data to draw a final conclusion that is warranted“).


I am thankful to the members of the sceptical group UFO-pragmatism for constructive discussions.


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