confusion. could there be a second shooter? >> the church committee concluded unanimously that there was at least two different gunmen but yet that's been denied by others. >> it may be the greatest mystery in american history. lee harvey oswald was ruled the only assassin. 60 years later, a gallup poll shows 60% of americans don't believe it. >> those are just a few of the stories that have long fueled speculation and a string of conspiracy theories. to learn more about them and read more of history's greatest mysteries, you, check out cnn.com. don? >> alexandra field, thank you very much. >> good evening. i'm don lemon. getting very close to the top of the hour, this is cnn's special live coverage of the disappearance of malaysian airlines flight 370. it is the boeing 777. it has missing for ten days with 239 people on board. here is what's new tonight in the search for the plane and the