This complaint, in context of bright spots appearing on the screen of an iPad, has been known to appear here with some regularity. This problem was often noted with the iPad Pro 10.5 - upon which the iPad Air3 is closely related. This is not to say that the problem is itself common, merely that the complaint appears to be common to these models of iPad.
Of complaints that have appeared within this community forum, the issue seems to focus upon bright patches (of varying intensity between affected devices) typically occurring in a region 1-2” above the Home button (as viewed with the iPad in the “Portrait” orientation - with the Home button at the bottom of the screen).
The bright patches appearing on the iPad Pro 10.5 / Air3 screen, where apparent, directly correlate to an area of the underlying logic board that incorporates the electrical connectors for the display - and the touchscreen controller. The bright patches are due to partial de-lamination of the screen backlight diffuser - due to heat; the brighter patches can spread over time.
Anecdotal comments (from reports appearing within this Support Community) suggest that when “inspected” by technicians, displays exhibiting this phenomena are generally considered to be fault-free - until such time as an inspection relates to a possible trade-in, at which point an affected screen has reportedly been described as having been damaged or defective, significantly reducing or eliminating any residual trade-in value.
The potential issue and its cause have never been publicly acknowledged by Apple.
