The dead fetus found on an American Airlines flight at LaGuardia Monday was left there by a pregnant Brooklyn teen, who suffered a miscarriage inside a lavatory as her twin sister stood guard outside that bathroom, law enforcement sources said late Tuesday. 
 
 The 18-year-old East Flatbush woman left the fetus behind on American Airlines Flight 1942 after it touched down in Queens on Monday night from Charlotte Douglas International Airport, sources said. 
 
 The flight landed and all the other passengers had deplaned when the pregnant woman rushed to the bathroom with her sister telling crew it was an “emergency,” law enforcement sources said. 
 
 A flight attendant told police the woman came out of the bathroom and looked ill, sources said. 
 
 The teen checked into Kings County Hospital at 12:30 a.m. on Tuesday and a cleaning crew made the gruesome discovery inside the Airbus A321 at about 7:30 a.m. at Hangar 5, sources said. 
 
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 Police want to interview the twins, but believe this was a miscarriage and not a criminal act, law enforcement sources said. The foot-long fetus was between three to six months along, sources said. 
 
 The City Medical Examiner is working on determining how the fetus died. 
 
 “The OCME can confirm we’re investigating what we believe to be a human fetus found deceased on an airplane,” the agency said. 
 
 A rep for American Airlines said employees are “working with law enforcement on an investigation.” 
 
 The airline later said in a statement: “As we continue to learn more about this tragic and sensitive situation, we are actively cooperating with law enforcement in its investigation.” ||||| A human fetus was found on an American Airlines flight on Tuesday morning. 
 
 American Airlines spokesperson Justin Franco told TIME that flight 1429 came in to La Guardia Airport from Charlotte, N. C., Monday and was parked overnight. A cleaner readying the flight so it could go back to Charlotte on Tuesday morning discovered the fetus, Franco said. 
 
 The cleaner notified a supervisor, who contacted law enforcement. 
 
 The New York City Chief Medical Examiner’s office is investigating the fetus to determine exactly how it died, a spokesperson told TIME. 
 
 Franco said the airline is “working with law enforcement to piece together what happened.” 
 
 “As we continue to learn more about this tragic and sensitive situation, we are actively cooperating with law enforcement in their investigation,” reads a statement from American Airlines. 
 
 The flight was delayed in returning to Charlotte on Tuesday morning, and passengers were accommodated, Franco said. The plane is back in passenger service now.
– American Airlines and New York authorities are investigating after a fetus was found in the lavatory of a plane that arrived at LaGuardia Airport from Charlotte, NC, on Monday. The plane was parked overnight before a cleaner discovered the fetus around 5am Tuesday, report CNN and Time. "As we continue to learn more about this tragic and sensitive situation, we are actively cooperating with law enforcement in their investigation," American Airlines says in a statement. The Queens District Attorney is investigating.