Some of us appear to have a very abbreviated sense of what is "right"
To posit that an airliner's Inertial Navigation System is "kinda like
GPS" is akin to stating that the aileron controls work like a steering
wheel! Neither approximation will get the ship safely to port.

Yours is a dangerous and irresponsible contribution.

The IRS system IS a system that provides positioning data of the
aircraft to the Flight Management Computer but is not as accurate as
modern GPS so my comments stand correctly. They perform the SAME
function but GPS use is more common now.
The 747-400 uses both an IRS and GPS data. NOTAMS will display which
countries are GPS certified. The Pilot must configure the Flight
Management Computer when flying over these countries so that the the
IRS positions aren't updated with an innaccurate GPS position

Ibby