Srinivasa S Erramilli, 46, a software consultant, has also been fined USD 5,000 and placed on court supervision for a year after he is released from custody by US District Judge Joan H Lefkow.
The judge set a hearing for next Wednesday on the government's request to revoke Erramilli's bond.
He is prohibited from airline travel while he is on supervised release and he is subject to deportation to India after being released from custody, the Department of Justice said.
In her order, judge Lefkow agreed with federal prosecutors that a custodial sentence was necessary to deter Erramilli and others from invading an individual's bodily integrity and also to ensure that victims of abusive sexual contact will be heard and given protection.
In fact, he has two previous convictions for nearly identical crimes.
According to Department of Justice, evidence at the trial showed that Erramilli was the last passenger to board a Southwest Airlines flight to Chicago's Midway Airport on June 14, 2011, and was seated in the only open seat available between the victim, who had chosen a window seat to sleep during the flight, and her husband, who had chosen an aisle seat to enable easier access during the flight.
The couple had travelled to Las Vegas for their 34th wedding anniversary.
The victim, now 65, who was wearing shorts during the flight, testified that Erramilli groped her three times aboard the plane.