A Muslim passenger was asked to leave an American Airlines plane after a flight attendant told him over the plane's public address system: "I will be watching you."
Mohamed Ahmed Radwan had boarded the flight from Charlotte, North Carolina, to Detroit, Michigan, last December when the announcement was made.
The Council on American-Islamic Relations (CAIR) has now filed a complaint to the US Department of Transportation, accusing American Airlines of "discriminatory conduct".
A letter from CAIR staff attorney Maha Sayed dated July 20 says: "As Mr Radwan took his designated seat, a female flight attendant loudly announced: 'Mohamed Ahmed, seat 25-A: I will be watching you'.
"The flight attendant was positioned in the aisle towards the rear of the plane and passengers in the vicinity heard her statement.
"After approximately one minute, the flight attendant repeated the announcement, this time stating: 'Mohamed Ahmed, that is a very long name, seat 25-A, 'I will be watching you'."
Radwan approached the flight attendant and questioned her about her remarks. She replied that she was watching everyone, the letter says, adding that Radwan was being "too sensitive".
"As a result of American Airlines discriminatory conduct," Sayed's letter continues, "Mr Radwan was compelled to book a significantly later flight that evening with a different airline company through his travel agent.
"Given the continuing rise of anti-Muslim rhetoric and hate crimes occurring throughout the United States, this type of reckless and harmful conduct should not be tolerated by our nation's airlines, which are legally charged with safely carrying all individuals who are rightfully present in an equal and nondiscriminatory manner, without regard to their religious affiliation or ethnicity.
"This is particularly troubling given the recent wave of incidents in which airline personnel have arbitrarily removed passengers of Muslim and/or Middle Eastern background without an objectively reasonable cause or explanation."
A spokesperson for the airline said: "American [Airlines] was contacted by CAIR earlier this year. We thoroughly reviewed these allegations and concluded that no discrimination occurred."
Following further conversations with American Airlines staff about the attendant's remarks, Radwan was eventually escorted off the aircraft.