What's the meaning of:

[ieasy]

I've read on CNN the following statement:
"Spacewalks for sale
Space tourists offered 'holy grail of spaceflight'"
I do not understand what does 'holy grail of spaceflight' mean. Can you explain it to me?

[Tetsuo]

Guess it meant to be described as something that people do not really know, to make it something special (more interesting), like advertising.. As a designer or creative person you need to find the right words to animate or create the intention / ambition to buy something that you at least do not really need. In other words to manipulate someone.

[DavyBCN]

http://en.wikipedia.org/wiki/Holy_Grail

It is a phrase used to search for something that is considered to be the ultimate prize.