OK.

Put one plane on one end of the conveyor belt.

Put another on the opposite end.

The conveyor belt counteracts the tires of one of them.

The other plane does not start it's engines. It will go with the conveyor belt.

Which will take off?

The one that has not started it's engines. The conveyor has pushed it through the air providing the pressure to cause lift.
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"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist