More than 650 people gathered in Colorado this month to promote the idea that our planet is as flat as a pancake.
Thousands were left perplexed by the high-altitude aircraft which circled for about an hour on Wednesday.
An anonymous metro area man submitted footage of the objects to a local news station for analysis.
Authorities are investigating a mysterious object that almost caused a mid-air collision last week.
Residents of Denver will vote in August to decide whether to set up a commission to investigate an alien cover-up.