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A former Chicago aviation security officer who was fired after forcibly removing a passenger off a United Airlines flight in 2017, has filed a lawsuit against the airline. In the picture, United Airlines planes sit on the tarmac at San Francisco International Airport, July 8, 2015. Getty Images/Justin Sullivan

A female passenger on a United Airlines flight accused her co-passenger of sexually assaulting her during a flight from New Jersey to Charlotte, North Carolina. The incident allegedly took place Tuesday, prompting an FBI investigation.

According to reports, the 37-year-old woman said she was sexually assaulted by the 73-year-old man seated next to her. The man allegedly placed his hands between her legs and groped her. The woman informed the crew about the man's behavior following which their seats were changed.

After arriving at Charlotte, police removed the man from the plane. According to a FBI spokeswoman the man was questioned but no arrest was made. The FBI is consulting with the U.S. Attorney's Office of the Western District of North Carolina on the case, the spokeswoman reportedly added.

United Airlines said that it was cooperating with the FBI in the investigation.

"The safety of our customers is our top priority, and we are working closely with authorities as they conduct their investigation," United said in a statement.

During questioning, the suspect told investigators that his hand merely fell on to the woman’s lap by accident, ABC-affiliated WSOC-TV reported. However, a fellow passenger said the man's account seems highly unlikely.

"I'm sure a woman knows the difference between a hand hitting her versus being groped," Sherrell Ealy said.

Another passenger aboard the flight recalled a flight attendant warning everyone after the flight landed to stay seated until police boarded.

"They said, 'Ladies and gentlemen, please stay in your seats. We have not been cleared to deboard the plane until authorities arrive,'" Genevieve Becker said.

Denise Bingham, another airline passenger, suggested to WSOC-TV: "I think some of these people should be checked, if they've been drinking, and not be allowed on a flight,"

This is not the first mid-flight groping incident that came to light in recent years. In July, a 28-year-old doctor was charged with engaging in sexual conduct with a minor after allegedly groping the teenager while she slept aboard a United Airlines flight.

So far this year, FBI officials have investigated 63 cases of sexual assault on planes compared to the 57 cases in 2016.