Officials say Prabhu Rama-Moorthy was sitting between his own wife and the alleged victim.
The woman said she had woken up to find her shirt and trousers unbuttoned and the suspect’s hand in her trousers.
Mr. Rama-Moorthy denied the accusations, telling police he was himself asleep after taking a pill.
Mr. Rama-Moorthy, an Indian citizen living in the US on a temporary visa, was sitting in the middle seat, with his wife on the aisle side and the alleged victim in the window seat.
The flight was on Spirit Airlines, travelling overnight and arriving in Detroit on Wednesday morning from Las Vegas.