Bewildered Student writes:

Just got an email [above] confirming a change in my flight number [from Amsterdam to Kuala Lumpar with Malaysian Airlines] from MH17 to MH19. People who have tickets booked for the flight and valid for travel until December 31, 2014, can cancel their flight and get a full refund  up until Thursday [July 24].

Malaysia Airlines retires flight number, offers full refunds following MH17 crash (CNN)