SEATTLE (AP) -- Robert Gribble has never  seen a UFO himself, but he
believes others who say they have and has investigated thousands of UFO
sightings for about 30 years.
   Gribble runs  the National UFO Reporting  Center from a  cramped but
tidy office in his home.
   "Even though  I've never seen one,  there's not the  slightest doubt
they're there," said  Gribble, a retired firefighter  recognized as one
of the country's foremost authorities on unidentified flying objects.
   "Either that or we've  got a lot of notorious liars  from all around
the globe," he said.
   He pays $1,200  a year from his  own pocket to keep  the center open
and fields an average  six calls a day from people  who think they have
seen unidentified flying objects.
   All  seek an  explanation.   Gribble  records their  comments,  asks
questions and takes their telephone numbers  in case he gets additional
information.
   "If people realize  we are not alone  -- as we have  been taught for
hundreds of years -- man's outlook as  to how we treat each other would
change," he said.  "Now  we think of ourselves as citizens  of the U.S.
If we  thought of  ourselves as  citizens of  the planet  Earth, things
would change for the better."
   Gribble's office contains  a large map of the  United States studded
with  3,500 shiny  red pinheads,  each representing  a so-called  close
encounter sighting of a UFO.  Some of the sightings date from 1946.
   A witness  must be within  500 yards of an  object to classify  as a
close encounter.
   Gribble  said he  wasn't surprised  by the  recent UFO  report of  a
veteran  Japan Air  Lines pilot  who said  his plane  was followed  for
nearly 400 miles  over Alaska by one gigantic and  two smaller aircraft
in mid-November.
   The  Federal Aviation  Administration later  confirmed  that an  air
traffic controller spotted the unknown  aircraft.  But agency spokesmen
say  their  investigation has  been  hampered  by a  radar  recording's
failure to show the aircraft's signal.
   From the  thousands of  calls he  has investigated  over the  years,
Gribble says most of the craft are described as disc-shaped, spherical,
oval, triangular  or cigar-shaped.   People reporting  close encounters
say a humming sound emanates from the object.
   The  government is  covering up  the  existence of  UFOs to  prevent
panic, said Gribble, who cites as evidence his own research and reports
from declassified government documents