The text states that entire groups of people have observed huge, complex mirages resembling cities in the sky.

The claim that entire groups of people have observed huge, complex mirages resembling cities in the sky is supported by the phenomenon known as Fata Morgana. This type of mirage is caused by atmospheric refraction and can create complex images of distant objects, including city-like structures. Evidence from sources such as Wikipedia and SKYbrary confirms the occurrence of such mirages, particularly in polar regions and over large bodies of water. Therefore, the claim is largely accurate based on the available evidence.