If we were not currently able to fly, but were on the verge of getting airborne, I have been thinking about what criteria I would use to determine unequivocally which new candidate was the first to fly a controllable and "practical" aeroplane.
Smooth and absolutely level surface
No manual pushing or towing and no mechanical assistance to help acceleration/take off
No headwind to increase lift
Consistent atmospheric conditions
Figure of 8 flight or two oval flights in opposite directions
Furthermore, the altitude above sea level that different candidates use to take off from would also have to be taken into account, perhaps all candidates should demonstrate take off at sea level and at several specified level heights above it
An international panel of experts to monitor, instruments to measure, and cameras to film and photograph each flight.
Only then could we establish which machine really was "practical" and capable of getting into the air and making controlled flight purely by its own power and design/construction.
With due respect to all the claimed first flights, they were not done in consistent/controlled conditions and I do not think that any of them would pass the sort of criteria and monitoring that the modern world expects of record breakers.