Judah wrote:
Where would I find out the total number of airplanes owned by all of the
airlines worldwide?

Take a look at the FAA registered aircraft databases. Pick out a
tail number on a commercial airliner (e.g. one of United's all end
in UA) and search. You'll find that almost none of the major
carriers own the equipment. It's handled thru leasebacks. Now,
the leasing company (that actually owns the aircraft) may also
be owned by the same holding company as the carrier (e.g. AMR owns
American Airlines, UAL owns United Airlines) but the carrier
itself doesn't own it.

If you dig far enough into the UAL website, you can find all
the odd companies that are owned by UAL, Corp. Fascinating!

And if you like that, dig into the Viacom list of companies...
That one's even more fun!