It's most likely they saw a projection of the plane, rather than they saw a ship utilizing technology that doesn't currently exist.

There's heavy shilling on the topic, I suspect that holographic technology, especially that which involves projecting crafts is top secret, or even a SAP. Could even involve that darn "Blue Beam" that ol' Skippy was talking about.

I don't blame you or your friend's parents for believing that alien tech is a possibility, but now that I've provided a logical explanation - let's see what happens.