Another jittery flight crew questioned the actions of a few Muslim passengers today, causing yet another flight to be delayed and police to question the four men.
As Northwest Airlines flight 243 from Amsterdam to Detroit -- the same route taken by a Nigerian man accused of trying to blow up a plane Christmas Day -- began its descent on Detroit, four passengers began to act in ways that alarmed their fellow passengers.
One or more of the men reportedly pulled a blanket over his head. When the plane landed at around 1:05 p.m., it was met by police.
Stay Up to Date on the Latest Travel Trends from ABC News on Twitter
In a statement sent to ABC News, the Transportation Security Administration said it was "notified of unruly passengers" on the flight. Federal authorities, including agents from Customs & Border Protection, Federal Air Marshals, and the FBI agents, held the plane from the gate for 15 minutes.
Customs officers questioned and then released the four passengers, whom other passengers identified as men of Middle Eastern descent in their 20s.
No arrests will be made in connection with the incident. Law enforcement offered no information on the passengers or their alleged actions.
Delta spokeswoman Susan Elliott said that "four passengers did not comply with crew-member instruction. Out of caution, the crew requested that authorities meet the plane upon landing." Northwest is a wholly-owned subsidiary of Delta.
"If it was serious at all," said Detroit Metro Airport spokesperson Mike Conway, "they would not have allowed the plane to taxi to the terminal."
This is just the latest in a string of panicked calls to police over incidents on planes that turned out to be nothing.
Last week, the Oregon Air National Guard scrambled two F-15 fighter jets after a passenger on a Hawaiian Airlines jet to Maui refused to let go of his carry-on bag and passed what was described as a "disturbing note" to a flight attendant.
Keoni Wagner, vice president of public affairs for the airline, called it a very "low-level" incident involving one disruptive passenger. Airport officals said the plane refueled and took off again for Hawaii. There were 231 passengers on board.
The passenger, a 56-year-old man from Salem, Ore., was eventually released without being charged after he was questioned by the FBI.
The day after Christmas, there was a scare also on a flight from Amsterdam to Detroit after a passenger, who had food poisoning, spent too long in the airplane's bathroom.
And last week, the Bakersfield, Calif., airport was shut down for several hours after a checked bag set off security alarms. A suspicious amber liquid in a passenger's bag initially tested positive for explosives, but it was ultimately determined that the substance was honey.
Also last week, a Northwest Airlines flight taxiing for takeoff at Miami International Airport returned to the gate after a passenger was heard making inappropriate remarks and acting disruptively. Local law enforcement and TSA met the aircraft upon its return and all passengers were deplaned.
The plane, bound for Detroit Wayne County International Airport, was swept, but nothing was found and it was cleared for departure.
With reports from Tahman Bradley