On Saturday, Katy Perry sent out a tweet commenting about the Malaysian Airline tragedy:
Well, it was quite a misleading tweet. Those 100 Unicef members she's referring to NEVER went on board.. She probably mistaken them with the 100 volunteers of the AIDS conference. UNICEF confirmed that her tweet connotes a misinformation, although there might be a few members that were planning to involve in the conference.
Katy Perry is the most followed celebrity on Twitter as well as the Goodwill Ambassador of UNICEF. As a "fabulous ambassador," probably would be the wisest to reconfirm some information with the organization ahead of tweeting.