dana larue sitting in the middle seat on a nighttime flight to chicago. the cabin dark. she fell asleep. >> i couldn't believe what was happening. >> reporter: she said the man on the aisle ran his hand up her leg. >> i was just stunned. i was stunned. >> reporter: then began touching her breasts. >> i was completely terrified and frozen. >> reporter: she said she felt trapped in the only after landing did she report the assault. she said too late for the fbi to gather evidence to arrest the man. >> i felt paralyzed and shocked. >> reporter: the d.c. field office of the fbi said it's investigated four similar cases in recent months. twice arresting the men accused and twice giving enough evidence to charge the guys. carlos vasquez flying from houston to dulles charged with assaulting a 15-year-old. he was rubbing her leg and thigh, up her orts, touching her underwear. the girl, court records say, pretended to be asleep. >> victims are so shocked that they're being assaulted so it takes awhile to process it. >> reporter: prosecutors say the victim pretended to sleep too.