Federal authorities say a French traveler’s first-class flight to Miami ended in handcuffs after a woman woke up to find him allegedly touching her on a Swiss International Air Lines trip from Zurich. Court papers state that 48-year-old Guillaume Sebastien Roger Mattler was seated next to the woman in first class, and other passengers reportedly captured parts of the incident on their phones. Mattler has already made an initial appearance in Miami federal court and is being held while prosecutors push to keep him detained as the case moves forward.
What investigators say
According to WPLG Local 10, an FBI agent wrote in a criminal complaint that two nearby passengers noticed Mattler touching the sleeping 29-year-old woman, and one of them recorded video on a cell phone. The complaint says a flight attendant saw Mattler with his hand on the woman’s crotch, over her jeans, making what was described as a scooping or rubbing motion. Another witness told investigators the movement looked like a “submarine” motion, as if he were trying to get his hand under her clothing. Crew members intervened, moved Mattler to coach, and separated the two. When the woman was awakened, she was reportedly crying and visibly shaken.
Court status and next hearing
Court records show Mattler appeared in Miami federal court on Wednesday, April 29, 2026, and is scheduled to return for a pretrial detention hearing on Monday, May 4, 2026. Prosecutors have asked that he remain jailed “based on (a) risk of flight and danger to (the) community,” according to WPLG Local 10. The complaint says Mattler initially denied any inappropriate contact, then later admitted touching the woman and told agents he had deleted photographs from his phone.
Federal charge and penalties
Mattler is charged with abusive sexual contact, a federal offense that covers unwanted sexual touching in situations under federal jurisdiction. The crime is set out in 18 U.S.C. § 2244, and the statute allows prison terms that vary by the specific conduct and subsection at issue, in many general cases sexual contact without permission is punishable by up to two years, while other circumstances in the law can carry longer sentences. For the statute’s text and sentencing framework, see LII / Cornell Law School.
FBI context and reporting guidance
The FBI has flagged sexual assault aboard aircraft as a growing problem and reported investigating more than 100 such cases in 2024, noting that these incidents most often occur on longer flights and in darkened cabins when people are sleeping. The bureau urges passengers and crew to report suspected in-flight sexual assaults to flight attendants and to the FBI and to preserve any evidence, including witness video, to help agents build cases. The FBI provides public guidance on how and when to report these incidents.
Why it matters here
Miami is a major international gateway, and the Southern District of Florida routinely handles sex-abuse prosecutions that fall under federal jurisdiction, which is a reminder that what happens on a plane can quickly turn into a federal case once the wheels touch down. The U.S. Attorney’s Office in the district has brought similar abusive sexual contact cases tied to travel and maritime settings, highlighting the local reach of these investigations. For instance, the Southern District has publicly outlined recent convictions in related cases, including one detailed earlier this year by the U.S. Attorney’s Office, Southern District of Florida.
Federal investigators say the probe into Mattler’s conduct is ongoing, and he is presumed innocent unless and until proven guilty in court. Authorities are asking anyone with relevant information to contact the FBI or Miami federal officials, consistent with the reporting guidance noted above.
