To begin- the photo you have here has been heavily touched up, making these sunken stone carvings appear to be raised copper figures.
These "images of modern-day helicopter, submarines, and UFOs" are not that at all (which should be obvious).
These are clearly palimpsests... When a pharoah dies and another takes his place, the new 'god-on-earth' often feels he must cover his ass by altering things that point at a previous 'god'. He hires some carvers to alter carvings in order to fit the current admin. This is stone- so alterations were fairly restricted, calling for heavy stylization of known glyphs.

Here is a more complete explaination...
http://www.ufocom.org/pages/v_us/m_archeo/Abydos/abydos.html