ORLANDO, Fla. -

Some pilots believe a flight bound for Orlando may have been a dry run for terrorists, according to a internal memo for a pilot's association obtained by WTSP-TV.

The Transportation Security Administration believes the September flight was an isolated incident.  But a memo from the US Airline Pilots Association, the union that represents US Airways pilots, shows flight crews are concerned plans for another terrorist attack could be underway.

According to the memo, the pilots say the most recent incident happened on Sept. 2 on US Airways Flight 1880, which was leaving Reagan International Airport in Washington D.C. and heading to Orlando International Airport.

Crew members said shortly after take off, a group of "four Middle Eastern men" caused a commotion. Witnesses claim a man ran from his seat in coach, toward the flight deck door and entered the bathroom for a considerable amount of time, according to the memo.

The three other men moved about the cabin, changing seats, opening overhead bins and generally "making a scene," the pilots association said.

TSA and US Airways both confirm there was an incident on the flight. When the flight landed in Orlando, TSA said the flight was inspected. All four men were detained and questioned but background checks produced negative results, according to TSA.