The following line should/could be removed from the script:

self endon( "disconnect" );

I added it because I'm used to write script like this for on the players and then it will be used but the ships don't disconnect from the map however players can .

I'm trying to do the same thing with rats, but I'm getting an error.

main()
{
  level thread rats();
}

rats()
{
  rats = getEntArray( "rat", "targetname" ); // Will get all the rats with rat as targetname

  for(i = 0; i < rat.size; i++) // Run the following on all the entities with rat as targetname
  {
    rats[i] thread rat();
  }
}

rat()
{

  // I've done it this way so it will be correct in the game!
  self.dest = (getEnt( self.target, "targetname" )).origin; // The rats target origin
  self.start = self.origin; // The rats original origin
  
  //wait 20; // Gave an error for some reason?!
  
  while(1)
  {
    //self playLoopSound( "m_engines" );
  
    self moveTo( self.dest, 60, 0.1, 0.1 );
    
    self waittill( "movedone" );
    
    self.origin = self.start;
    
    wait 20;

  }
}

The error:

uninitialised variable 'rat'
  for(i = 0; i < rat.size; i++) // Run the following on all the entities with rat as targetname

Check carefully you entity assignments (i.e. rats = getEntArray("blah", "blah" ) is an entity assignment, where "rats" is assigned (=) to the entarray()).

In this case, change rat.size to rats.size.

Thanks Demon, that fixed it