I was on my way to a bunker in archipelago region when it came up with relay beacon. it was a plane surrounded by 3 different types of hunters. I killed them all but what was the plane there for- what is a relay beacon?
Thanks
Planes are just props. There sometimes are dead pilots in the cockpit - you can loot them.
Destroying relay beacons give you a lot of XP (500-1500) and a radio.
ok thanks what is best way to destroy them
Just shoot them until they explode 
Shoot the yellow fuel tanks at the top.
Guide for taking out relay beacons in the most cost effective way, in here: Tips for fast XP gain for solo players