On September 4, 1957 at 19:21, four bomber aircraft took off the Ota Air Base, in Portugal. They were under Captain José Lemos Ferreira's control. The other pilots were sergeants Alberto Gomes Covas, Salvador Alberto Oliveira and Manuel Neves Marcelino. The first part of the operation was successful, and so they turned towards the city of Portalegre. At this point, Captain Ferreira noticed a strange light above the horizon. After observing it for 3 or 4 minutes, he warned the others about what he had just seen. The pilot on his right had already seen it. The object looked like a very shiny star, but much bigger than normal. Its center changed colors constantly, going from green to blue, with some yellow and red tones.
On September 10, 1990, around 9:30AM and for about 50 minutes, a small "balloon" was seen hovering towards a small football field, on a small village called Alfena in the outskirts of Porto. The object was described as "a small turtle with long legs" with a metallic shine. The people present got scared and a group of construction workers started throwing stones at it, and the object hovered backed away, leaving the site. An amateur photographer took several pictures of the shapeshifting object; the pictures were considered by several experts as real and the witness accounts by the simple folks were not considered hoax.