A White House plane carrying Michelle Obama came dangerously close to a 200-ton military cargo jet and had to abort its landing at Andrews Air Force Base on Monday as the result of an air traffic controller’s mistake, according to federal officials familiar with the incident.

Ultimately, controllers at Andrews feared that the cargo jet was not moving quickly enough to clear the runway in time for the White House plane to land, said the officials, who spoke on condition of anonymity because they are not authorized to speak for their agencies.

Officials with the Federal Aviation Administration confirmed Tuesday that the first lady was aboard the plane and said that “the aircraft were never in any danger.” The White House referred all questions to the FAA.

The FAA, already dealing with a series of controversies involving controllers sleeping and watching a movie on the job, sent a team of investigators Tuesday to the Warrenton radar control center, where the mistake was made.

The number of air traffic controller errors where planes come too close to each other have increased dramatically in the past year. They still account for only a tiny portion of all flights, and very few of the errors put passengers at risk. The FAA classified Monday’s error as an “A,” the most serious type.

The first lady was returning from a television appearance and other events in New York with Jill Biden, the vice president’s wife, and was aboard a Boeing 737 that is part of the presidential fleet when the error occurred on the plane’s final approach to the base.

The FAA controllers in the tower at Andrews recognized that the massive C-17 and the Obama flight were far too close when the Warrenton controller handed off responsibility for the two aircraft.

They ordered the Obama plane to execute a series of S-turns in an effort to create a safe distance between it and the C-17, federal officials said. When those maneuvers failed to achieve the required distance between the two planes — and the Andrews controllers realized the cargo jet would not have time to get off the runway before the presidential plane arrived — they aborted the landing of the Obama plane and ordered it to circle the base.

The correct distance

Because an airplane’s wake causes severe turbulence and, in extreme cases, can cause a plane that enters into it to crash, the FAA has strict standards on how much distance controllers should maintain between planes.

A fully loaded C-17 can create such turbulence that the FAA requires other planes to remain at least five miles behind it. The presidential fleet 737 already was far closer than that when the handoff took place from the Potomac Terminal Radar Approach Control (TRACON) facility in Warrenton.

“The manager and tower controller at Andrews did several things to try to increase the separation on final [approach] before ordering a go-around,” said a senior FAA manager familiar with the incident.

The FAA manager said the Warrenton controller exhibited “really bad controller technique.”

“Not only did he get them too close, he told the [Andrews controller] that they were farther apart than they were,” he said.

When the handoff occurred, the planes were 3.08 miles apart, radar shows, but the Warrenton controller told the Andrews tower that they were four miles apart. Before handing off, the Warrenton controller warned Obama’s pilot of potential wake turbulence.

In the Andrews tower, controllers had already identified “a serious loss of separation” but were reluctant to contact the Warrenton facility to point it out, officials said.

The Andrews controllers ordered the S-turns as soon as they assumed responsibility, but the two planes still grew closer. Finally, fearing the cargo plane couldn’t get off the runway in time for the Obama plane to land, they ordered the 737 to abort the landing attempt.

“In the grand scheme of things, events like this happen fairly frequently,” said another federal official who works with the air traffic control system but is not authorized to speak publicly. “Unfortunately, this one involves a presidential plane.”

Directing traffic

Both go-arounds and errors by air traffic controllers are not uncommon. Controllers at Potomac TRACON, who direct more than 1.5 million flights a year to area airports, made a record number of errors in 2010.

Nationwide, recorded errors by controllers increased 51 percent last year to 1,869.

The Potomac facility recorded 52 controller errors, an increase from 21 recorded in 2009. In a memo to his staff last year, the center’s director cited “a definite increase in sloppy or poor adherence to SOP [standard operating procedure] and handbook procedures.”

In most instances — both locally and nationally — planes came too close but without risk of collision; in some, however, fatal consequences were narrowly averted.

The go-around is seen by controllers as a fairly routine safety procedure that keeps planes out of greater trouble.

In October, Reagan National Airport recorded 39 go-arounds, Dulles International Airport had 20 and Baltimore-Washington International Marshall Airport had three, according to an internal FAA document. In August, FAA records show at least seven instances in which planes on final approach to National were ordered to go around “due to traffic on the runway.”

That traffic on the runway could be there because a plane that just landed hasn’t moved out of the way quickly enough or, more likely, a plane cleared for takeoff has dawdled on the runway past the time when the controller expected it to be gone.

In 2010, the National Transportation Safety Board took an unprecedented step by beginning to investigate the most serious mistakes by air traffic controllers.

Among the cases under NTSB review are near-collisions between a Boeing 737 and a helicopter in Houston; a Boeing 777 and a small plane in San Francisco; and an Airbus 319 and a Boeing 747 in Anchorage.

Another case under review is an incident last year near National that involved an airliner carrying a congressman. Rep. F. James Sensenbrenner Jr. (R-Wis.) demanded an explanation from the FAA after his United Airlines flight bound for National swerved to avoid another jet after the encounter activated the onboard collision-avoidance system.

Staff writer Nia-Malika Henderson contributed to this report.