“I’m so sorry I’m scared now,” she posted, insisting variously that her original message had been a joke; that it had emanated from a friend’s Internet protocol, or I.P., address; and that her account had been hacked. “My parents are gonna kill me if I tell them this omg pls,” she wrote, before adding: “I need a lawyer. Any lawyers on here?”

The Rotterdam Police Department said Tuesday that she could face criminal charges for posting a false or alarming announcement. Tinet de Jonge, a spokeswoman for the department, said by phone that the girl had been released Monday but remained a suspect, pending an investigation. She said it was up to American Airlines to decide whether to press charges. “Some people think it’s fun to send a threatening message on Twitter,” she said. “But American Airlines didn’t think it was funny at all.”

Matt Miller, a spokesman for American Airlines, declined to comment on how the carrier might proceed. “The safety of our passengers and crew is our top priority,” he said Tuesday. Dozens of threatening copycat tweets had been sent to the airline by Tuesday.

As the exchange spread online, the girl acquired thousands of new followers and appeared to at least momentarily revel in the attention. She offered to auction her Twitter handle, and suggested $500 as the starting bid. “I feel famous omg,” she wrote. Her Twitter account has since been suspended.

The girl’s father defended her, telling the Dutch newspaper Algemeen Dagblad on Tuesday that his daughter was a typical teenager, not a criminal. “It was just a joke, from a girl who should have been doing her homework,” he said. He said he had not been aware that she had drawn global attention. “World news? I had no idea,” he told the newspaper.