you cannot announce it. there are millions of idiots that'll jump off bridges, stop going to work, and riot/loot cause they think the world is ending. People are fcking distracted enough as it is... driving 15 mph over the limit on their phones texting like the Constitution says they are allowed.
As much as I'd love to learn more about UFOs, any admission by govts would be vague, and the result would just be morons speeding and texting AND taking selfies of the sky as they drive.
Note: I'm waking up to another weekend of accidents in SW FL, including one where a 10 year old was ejected from a car and killed, and just plain tired of idiot fcking drivers.