Norfolk District Attorney William Keating cited evidence including a handprint in the wheel well, clothes strewn along the plane's flight path and an autopsy report indicating the teen fell "from a significant height."
Keating said Friday that he had informed federal transportation safety officials about the apparent airport security breach by 16-year-old Delvonte Tisdale.
"To withhold any information at this point I think would endanger public safety," said Keating, a Democrat who was elected in November to represent Massachusetts' 10th Congressional District.
Keating held a news conference Friday after police searched a wooded area in Milton near where Tisdale's body was found last month. Along a path a Boston-bound plane would have taken while approaching the city, they found dark sneakers with white stripes and a red shirt matching clothing Tisdale's family said he'd worn, Keating said. Keating said an autopsy showed trauma to Tisdale's body "was consistent with a fall from a significant height."
Investigators also discovered a handprint in grease inside the wheel well on the left side of a Boeing 737 that took off from Charlotte Douglas International Airport in Charlotte, N.C., on Nov. 15, the night Tisdale's body was found, Keating said.
"We feel it's important to inform federal transportation safety officials that it appears more likely than not that Mr. Tisdale was able to breach airport security and hide in the wheel well of a commercial jet liner without being detected by airport security personnel," Keating said.
Keating called what happened to Tisdale "a terrible tragedy."
"But if that was someone with a different motive, if that was a terrorist, that could be a bomb planted on there undetected," Keating said.
Jon Allen, a spokesman for the Transportation Security Administration, said: "We will work with the airport, which is responsible for access control security, to conduct a thorough investigation based on the facts and information provided by law enforcement."
Tisdale was a member of the Air Force ROTC program at North Mecklenburg High School near Charlotte. His father, Anthony, said the family had moved from Greensboro to Charlotte in the summer so the teen could join that program. Anthony Tisdale said his son was happy in Charlotte and stayed out of trouble.
But Delvonte Tisdale's brother, Anthony Tisdale Jr., said his brother was unhappy in North Carolina and had never wanted to leave Baltimore.
Delvonte's grandmother, Lula Mae Smith, said Friday evening from her home in Baltimore that she hadn't been told about the prosecutor's finding.
"This is a surprise," Smith said. "He was such a good boy. I don't know what happened — why he would jump on an airplane. I just don't know."
Laura Attikou, Delvonte's aunt, said her brother's son was well-behaved and had a good life.
"The biggest mystery to me is how did he get on that plane? Where was security?" she said from her home in Greensboro, N.C. "We're still at a loss. We're still in shock."
Keating said Tisdale was last seen by a sibling at home in North Carolina at 1:30 a.m. The flight he's believed to have boarded took off at about 7 o'clock that evening, and investigators confirmed flight times and paths with the Federal Aviation Administration, he said.
Just before 9 p.m., someone who lived near where the body was found heard a loud crashing noise, Keating said. At 9:30 p.m., Tisdale's body was discovered without shirt or shoes by a group of college students in Milton, an affluent Boston suburb.
Keating said his office first tried to determine whether Tisdale was a crime victim. The body was found after apparently being run over by a Jeep and then an Audi, and investigators found blood and tissue on the undercarriages of both vehicles. But Keating said there was no proof of a hit-and-run, Keating said.
He said police also interviewed family members in North Carolina without finding a "scintilla" of evidence of foul play.
Last week, detectives visited the Charlotte airport to take samples of grease used in maintaining the planes, to see if it matched grease found on Tisdale's pants. (The tests have not been completed.) That's when they found scuff marks and the handprint in the wheel well, Keating said.
Keating acknowledged initially that it seemed like a remote possibility that a teen could sneak onto a commercial jet.
"This wouldn't be the first [possibility] a person would think about," he said.