The woman was sitting in the window seat next to the man, Prabhu Ramamoorthy.
Federal prosecutor Amanda Jawad said Ramamoorthy stopped after the victim opened her eyes and then the shaken woman immediately alerted flight attendants. In July 2014, a 19-year-old female passenger on Delta Air Lines en route to Amsterdam from Detroit a couple years earlier had fallen asleep midflight, only to wake up and discover the man seated next to her had his hands down her underpants and was fondling her, according to a criminal complaint filed at the time in federal court in Detroit.
His wife told officials a similar story, and said that they had called the flight attendants to try to change seats. But the prosecutor said that "flight attendants did not report that anyone asked them to change seats other than the victim".
Ramamoorthy gave "conflicting reports", about what happened with the victim, Jawad said.
Magistrate Judge R. Steven Whalen ordered Ramamoorthy jailed ahead of a detention hearing.
The entire incident took place in presence of the wife of the accused, who was sitting next to him.
Ramamoorthy's lawyer, Richard O'Neill, had offered to turn over his client's passport.
"There's been no allegations from anywhere that his behavior has ever been inappropriate prior to this incident", O'Neill said.
According to the Association of Flight Attendants-CWA, a union for flight attendants, one out of five flight attendants surveyed from a group of 2,000 a year ago said they had received a report of a passenger being sexually assaulted. The police were contacted less than half the time, the survey found.
In the USA, the number of sexual assault cases has only increased in the last few years.