Flight formation of 20 or more bright white objects over San Salvador, El Salvador.

During December, 1983, at or around 8:00PM.
 Myself age 13, and 3 other adults were on the terrace of our two story house.  It was a pleasant night and we were looking up while lying down on patio lounge chairs.
 In the clear night sky appeared around 20 or more very intensely bright white stars.  They appeared suddenly, one after the other, some would pop out of existing ones; almost as if someone had turned on a light switch and a light bulb was turned on.  They were all white globes in appearance, closely resembling the brightest stars in the sky, but without the telltale blinking of a star.
 At first there simply hovering at what I consider to be the height of a high flying airliner.  After the last one appeared, they organized themselves into a square formation, a very precise flying formation.  Soon after, they started flying very slowly away from our observation post.
 They suddenly stopped before they were to disappear from our field of view and started to do what I can only describe as flight maneuvers, such as what the Blue Angels would do; all in a tight formation.  It's interesting to note that they would suddenly stop and make very quick turns; all in formation.  After about 20 minutes of this, they disappeared in the very same way that they appeared: they suddenly extinguished themselves.
 It's interesting to note that we had an AM radio playing music at the time, but there seemed to be very heavy interference while these objects were in the sky.  I would also like to note that there was a heavy military operation being conducted in the country, but I would not be able to say if that was in any way related to what I saw.
 I am not claiming what I saw were UFO's, but I had never, and have never since, seen anything of that sort.
Witness indicates that the date is approximate.  PD