Erramilli, a software consultant, was sitting in a middle seat between the woman and her husband as the couple returned from Las Vegas where they had celebrated their 34th anniversary, the victim testified during the three-day trial in Chicago.
The victim was awake when Erramilli touched her a third and final time, and she began hitting him and calling him either "a pig" or a "pervert," she told jurors. Other passengers testified they also heard the woman yell, "Get your hands off of me!"
Jurors heard key testimony that Erramilli was convicted in 2002 and sentenced to probation after grabbing a woman's breast on a Detroit-bound flight. In 2000, he was sentenced to two years of probation for a similar incident.
Those previous convictions will be factors when U.S. District Judge Joan Humphrey Lefkow sentences Erramilli on April 26. He faces up to two years in prison and a maximum fine of $250,000.
A spokesman for the U.S. Attorney's Office in Chicago, Randall Samborn, praised the victim for coming forward and testifying.
"Passengers on an airplane should be free to travel without having to be victimized by this conduct," he said.
The office of Erramilli's defense attorney, Timothy Roellig, said there would be no comment.
As the verdict was read on Thursday, Erramilli showed little emotion but later sat with his head bowed. A relative of his wiped tears from her eyes.
During the trial, the victim explained that she chose a window seat so she could sleep, while her husband sat in an aisle seat for easier restroom access. Erramilli was the last passenger to board the plane and was given the only open seat left — between the couple.
The victim awoke a first time after she felt something brush against her thigh and then a second time after feeling greater pressure against her leg, she testified. She was awake when Erramilli grabbed her thigh.
According to court documents, Erramilli had pleaded with flight attendants not to call police after the plane touched down at Chicago's Midway Airport, telling them his wife and children were meeting him at the airport.
Prosecutors asked Thursday that Erramilli be jailed immediately pending sentencing, saying he had close family in India and was a flight risk. But Lefkow ruled he could remain free, though he is barred from air travel and can on make business trips by car.