Thanks to Greg Reeder for forwarding extracts from Zahi Hawass's latest report in the HORUS in-flight magazine of EgyptAir, March/April 2006, pages 19-21. Unfortunately there's no online version, but in an article called The Search for Nefertiti continues in the Valley of the Kings Hawass describes how he was notified of the discovery of the shaft leading to KV63, and that the decision to make an announcment was deferred until something more was known about the contents of the shaft and what it lead to. He also discusses the issue of the concession having been formerly under the supervision of the Amarna Royal Tombs Project. The article is well worth a read if you find yourself flying on EgyptAir before April!
Here's a short quote from the article: "This year, before they began their season, Drs. Schaden and Corcoran came to me and we discussed together the future of this shaft. Their team began at the beginning of January to dig, removing sand and stone rubble. At the end of January, I went to the Valley of the Kings to visit their work. Dr. Schaden showed me that the architectural style of the shaft is 18th Dynasty, the era when Tutankhamun was king. There had been Dynasty 19 debris above it, which means that it may have been visible to those who came in that period. On the other hand, the 19th Dynasty teams may have covered the shaft without noticing it. It is most likely in either case that no one saw it after the 19th Dynasty."