It’s not absolutely clear who was uneasy that two Muslims wearing traditional clothing had boarded Atlantic Southeast Airlines Flight 5452 to Charlotte, N.C., but it’s evident someone was.

The two men – one an adjunct professor of Arabic at the University of Memphis and the other an imam at the Islamic Association of Greater Memphis – were already in their seats Friday and the plane pulled away from the gate when they were asked to deplane, according to news reports.

Atlantic Southeast Airlines, a regional partner of Delta, said in a statement only that the flight "returned to the gate to allow for additional screening of a passenger and the passenger's companion. We take security and safety very seriously, and the event is currently under investigation." The carrier also apologized for any inconvenience to the travelers.

Ground zero and beyond: four mosque battles in the US

The men, who were on their way from Memphis to North Carolina for a conference of North American imams where Islamophobia and anti-Muslim bias were to be discussed, cooperated with authorities, were rescreened, and booked on a later flight.

One of the travelers, Prof. Masudur Rahman, said Delta officials reported that the pilot, not fellow passengers, was the one who was uncomfortable with his presence and that of his colleague, according to a Reuters report.

There was some speculation that the plane returned to the gate because the pilot had heard that some passengers were worried. However, the pilot is reported to have refused to allow the two Muslims to reboard the plane after additional screening and left without them.

A passenger on board the flight told the Atlanta Journal Constitution that, upon arrival in Charlotte, the pilot said the Transportation Security Administration (TSA), which is in charge of airport security, had requested that the plane return to the terminal. He also said he did not notice discomfort among the passengers.

TSA officials say its agents escorted the men off the plane and searched the area around their seats, but that the airline, not TSA, had not initiated the extra screening.

"I don't know what kind of pilot he was, I don't know his mentality," Dr. Rahman told the Memphis Commercial Appeal. "I think some action should be taken so this won't happen with other people, any religion, any person, any professional."

There have been previous incidents of Muslim passengers reporting bias at commercial airlines, including passenger wariness. In many places across the US, security has been tightened this week out of concern of retaliation for the US commando raid that killed Al Qaeda leader Osama bin Laden.

Former NPR news analyst Juan Williams lost his job back in October when he said during a guest broadcast on Fox News: “When I get on a plane ... if I see people who are in Muslim garb and I think, you know, they’re identifying themselves first and foremost as Muslims, I get worried, I get nervous.”

Rahman, who said he and his fellow traveler were nine hours late to their destination, found a teachable moment in the ordeal. He noted in the Reuters interview that both of them had been cleared by security, and suggested the pilot may not have understood much about Islam and how Muslims typically dress with their bodies fully covered. "People are losing freedom," he told Reuters.

Ground zero and beyond: four mosque battles in the US