Washington:
An Air Force passenger jet carrying Michelle Obama to Andrews Air Force Base early Monday evening had to abort its landing and circle the field because it was following too closely on the tail of a giant military cargo plane arriving ahead of it, the Federal Aviation Administration said on Tuesday.
The plane carrying the first lady, a military version of a Boeing 737, was three miles behind the C-17 but was supposed to be five miles behind, because of the possibility of encountering turbulence from the cargo plane's wake. The planes were too close because of an error by a civilian air traffic controller at a low-altitude control center in Virginia, according to a government official involved in following up the incident. But the official described the event as "routine."
The controller in Virginia, handing the approaching plane off to the control of controllers in the tower at Andrews, at first misstated the distance separating the two planes, saying that they were four miles apart when in fact the gap had closed to three miles, the official said.
To try to spread the planes apart, controllers ordered the plane carrying Mrs. Obama to maneuver in broad turns like the letter S, as one skier would do to avoid coming up on another too quickly from behind.
But that was not enough, and the controllers in the tower at Andrews ultimately ordered the Boeing to "go around" because they were concerned that the cargo jet would not have time to touch down, decelerate and exit the runway on a taxiway before the passenger plane crossed the runway threshold. That problem occurs dozens of times a day with airliners at civilian airports around the country, according to aviation experts.
The incident occurred just after 5 p.m. on Monday, the F.A.A. said in a statement, adding that "the aircraft were never in any danger." The agency did not say in its statement that the problem was controller error.
The incident was first reported on the Web site of The Washington Post.
Airliners sometimes execute "go-arounds" because a pilot in the cockpit judges that the plane in front will not clear the runway soon enough; in this case, it was controllers in the tower at Andrews who ordered the plane carrying Mrs. Obama to go around. Although Andrews is a military field, all the controllers involved in this incident were F.A.A. employees.
"Go arounds" follow pre-established procedures that give the direction to turn and the altitude to which the plane should climb.
Following a big aircraft like a C-17 too closely is considered particularly risky at low altitude, when an upset would be more likely to lead to a crash. In this case, the altitude of the 737 was not immediately clear, but it was more than three miles from the runway threshold, because it was more than three miles behind the cargo jet and the cargo plane had not yet reached the runway, according to the government official.
While the aerial choreography in this case was not unusual, it comes after several weeks of high-profile problems in the air traffic system, which began in the Washington area.
On March 23, the sole controller on duty in the tower at Ronald Reagan National Airport, in Virginia across the Potomac River from Andrews, fell asleep at his post, and two arriving planes were unable to contact him. Both landed anyway. The controller on duty at the Reno-Tahoe International Airport in Nevada also failed to respond to calls from an incoming aircraft last week. And on Thursday, the official in charge of air traffic control, Henry P. Krakowski, the chief operating officer of the agency's Air Traffic Organization, resigned.
At the time, the administrator of the F.A.A., J. Randolph Babbitt, said in a statement: "Over the last few weeks we have seen examples of unprofessional conduct on the part of a few individuals that have rightly caused the traveling public to question our ability to ensure their safety. This conduct must stop immediately."