Feds probe mysterious markings on Southwest jets
Per the article:
Federal agencies were working with Southwest Airlines on Thursday to determine who has been vandalizing their aircraft with mysterious markings, CBS Radio reports.
Since February, several Southwest jets have been vandalized with mysterious writings that show up on the underbelly of their 737 passenger aircraft. The writing was done with a chemical process that reveals the text once an auxiliary power unit is turned on and heats up the outside skin of the aircraft.
Southwest Airlines has ordered its employees not to discuss the matter with the media.