Left Andy's custard on rangeline. Headed north to home and noticed what we though was a medflight. It flew smooth and slow. Dropping quickly like it was going to land. Thought we would go rubber-necking to see if there was an accident. As we got to 20th and rangeline we noticed it didn't look like a helicopter or anything we could identify. As we turned onto texas ave. literally chasing this "thing" and it looks as if its about to land in someones backyard it vanishes. We drove around for a half hour trying to explain where it went and it dissapearred from our sight out of thin air. If I didn't have a passenger with me seeing as well I would have thought I was seeing things. It was completely silent.