Abydos helicopter

The Abydos helicopter (a.k.a. the Abydos Submarine, the Abydos Jet Plane, the Abydos UFO, etc.) is a pseudoscientific modern myth that has been spread rapidly via the Internet concerning the singular appearance of a re-carved inscription in the mortuary temple of Seti I in Abydos, Egypt.

It is claimed this carving depicts various high-tech or alien technologies, such as submarines, jet planes, and UFOs, thus playing into the theories that Ancient Egyptian civilization was either influenced or founded by aliens or Atlanteans.

Historical background
The temple was built during the 19th Dynasty of Ancient Egypt, in the post-Amarna New Kingdom. It was built as a cenotaph and mortuary temple for Seti I, linking him to the cult of Osiris, which had a major presence at Abydos, and the temple features a prominent Osiride theme throughout, although other deities, as well as Seti I himself, were worshipped here. The temple was not completed in the lifetime of Seti I, but was completed by his son, Ramesses II, early in the reign of the latter. The work of Ramesses II was inferior to that of his father, and it is easy to tell, even without reading the temple inscriptions, in which reign each section was completed. As a result of this "shoddy" work, some inscriptions were re-carved, hastily chiselled out, modified using plaster infill, or even just plastered over and new inscriptions chiselled into the plaster, which over millennia crumbled or dried, falling away from the stonework.

Conspiracy nuts, UFO theorists, and Egyptologists
It's claimed the name of the temple "Temple of SETI" is a dead giveaway.

It is also claimed that the inscription in question depicts various advanced technologies, such as jet aircraft, UFOs, helicopters, and even submarines, although no effort is ever made to explain the practical use the latter would have in the Nile, the most important waterway to the Egyptians, notable more for its shallow depth and sandbanks than its abyssal depths and submarine warfare raging beneath the papyrus skiffs of the commoners.

The existence of these inscriptions is used to "prove" such technology was known to ancient civilizations, which is then often used as "proof" for alien or Atlantean involvement in the early development of ancient civilizations.

Egyptologists dismiss such claims, and regard the Abydos inscription as a simple case of a filled and re-carved titulary, something which is commonly seen in Egyptian temples.

Evidence
Generally, only two or three photographs of the inscription circulate to back up the "Abydos Helicopter" argument. One of them appears to have been digitally "cleaned" to make the inscription look much "tidier" than its actual state. This itself has raised several eyebrows in academia, and the low resolution of the images supplied as "proof" does nothing to sway those concerned with academic concerns over "creative" interpretations of Egyptian history. The inscription itself is actually in the dark recesses near the temple roof, and is in fact almost impossible to see with any degree of clarity from the ground.

The lack of any surviving examples of the craft that the advocates of the Abydos Helicopter claim the inscription depicts is no deterrent to the belief. Neither is the lack of any other inscription in any other Egyptian monument whatsoever, nor any mention of said craft in any Egyptian literature whatsoever. Nor indeed, any mention of the Atlanteans/Little Green Men who brought such technology to them. The silence of the ancient Egyptians on this crushing and awe-inspiring degree of technology compared to their rivals is curious, given their unending enthusiasm for characteristically immodest statements of their own greatness and superiority over foreign rivals.

The case for re-carving is overwhelming. Not only are there innumerable examples of exactly the same practices being employed at other sites throughout Egypt, but reconstructions of the original and modified texts, prior the deterioration of the plaster layer, have also been prepared to make an entirely rational and plausible argument for the alteration of the titulary of Seti I to that of Ramesses II.

To summarize, therefore, we can conclude that the "Abydos helicopter" is, in fact, irrational bullshit.