I heard NASA is considering re-categorizing the Space Shuttle into the "Experimental" category because it hasn't gone through the hundreds of test flights that conventional aircraft must endure.
Also, if you look closely at pics of the 777-300ER, you can see the word "Experimental" painted above the door, which was strange to me because I'm not accustomed to seeing this on such large aircraft. I see it on homebuilts all the time, however.