An investigation is underway today to determine what precipitated air traffic controllers' allowing first lady Michelle Obama's plane to come too close to a military cargo plane, forcing it to abort its landing and rekindling some anxiety among the flying public.
The plane, carrying Obama and the vice president's wife, Jill Biden, eventually landed safely at Joint Base Andrews Monday, officials said. The incident is one of several recent mishaps involving air traffic controllers, including those in which controllers have been caught falling asleep and watching movies on the job.
But Aviation expert and ABC News consultant John Nance said there's no need to fear flying. "The basic problem is it's a human system ... we expect perfect performance by humans a 100 percent of the time, Nance said.
"Whenever you build a system to expect that kind of performance, you're going to be disappointed over and over again. We've got great people in air traffic control but we really have historically expected too much of them."
Michelle Obama and Jill Biden were returning from making several appearances in New York Monday when air traffic controllers apparently allowed the planes to get too close to each other. The required separation is five miles but controllers allowed the Boeing 737 that was carrying the two women to come within three miles of the giant C-17 military cargo plane, Federal Aviation Administration sources told ABC News.
The distance is important because large planes generate wake turbulence, the equivalent of two miniature tornadoes streaming off the plane. The rough air dangerously disrupts the plane behind it.
"If this hadn't been an aircraft as big as a 737, it could have been very significant because those horizontal tornadoes … can upset a smaller airplane," Nance said. "A 737 would have a bit of a problem but nothing really terribly lethal. The problem is you don't want this kind of operational error anywhere anytime and they unfortunately do occur."
Air traffic controllers handling Obama's plane, dubbed Executive One Foxtrot, ordered the pilot to do standard S-turns to create the appropriate distance, which they did.
"Can we slow down for executive one foxtrot," the air traffic controller said in audio obtained by liveatc.net.
Even after the military cargo plane landed, though, the controllers were reportedly still worried that the C-17 wouldn't clear the runway in time for Obama's jet to land. The air traffic controller ordered the first Lldy's pilot to abort the landing and circle the airport.
There was no panic caused by the incident and no emergency vehicles were called in. No one on the plane, including the first lady, was aware of the delay or the high-sky maneuvers, sources said.
"FAA controllers at Andrews Air Force Base instructed an incoming Boeing 737 on approach to Runway 19 to perform a 'go around' on Monday, April 18, 2011 just after 5 p.m. because the plane did not have the required amount of separation behind a military C-17," the FAA said in a statement. "The FAA is investigating the incident. The Boeing 737 landed safely after executing the go around. The aircraft were never in any danger."
The first lady was returning to Washington, D.C., from New York, where she appeared on "The View" with Biden and attended other events Monday.
The incident comes at a time when air traffic controllers are already under scrutiny.
There have been at least five reported incidents of air traffic controllers falling asleep on the job in the last two months, which has prompted negotiations between the government and the controllers' union to change the way controllers are scheduled to work.
The FAA has acknowledged there is a widespread problem with fatigue among controllers and that the agency is taking steps to improve the situation, including an additional hour of rest and changing their schedules so they cannot work a three-day weekend.
Transportation Secretary Ray LaHood told ABC News today he is "hopping mad" about these recent incidents and that the agency "will just not tolerate it from our controllers."
"Guiding planes full of people in and out of airports is serious business. And so my reaction is I'm hopping mad about it and we will continue to suspend controllers and doing investigations until we put a stop to this," he said. "My idea is zero tolerance for this kind of behavior -- zero."
Feb. 19: A controller in Knoxville, Tenn., went to sleep on the job during a midnight shift. Sources told ABC News that the controller made a bed on the floor of the control tower with couch pillows.
March 23: A controller on his fourth consecutive overnight shift at Washington, D.C.'s Reagan National Airport left the radio tower silent after apparently falling asleep. Two commercial airliners were forced to land on their own.
March 29: Two controllers at Preston Smith International Airport in Lubbock, Texas, did not hand off control of a departing aircraft to another control center and it took repeated attempts for them to be reached.
April 11: A controller at Boeing Field/King County International Airport in Seattle fell asleep on the job. Boeing Field does not handle any commercial air travel.
April 13: A controller at the Reno-Tahoe International Airport in Nevada was sleeping as a plane carrying a crticially ill patient was trying to land.
April 16: An air traffic controller fell asleep on the job at an air route control center in Florida.
April 17: An air traffic controller near Cleveland was suspened after being caught watching a movie -- Samuel L. Jackson's "Cleaner" -- on the job.
ABC News' Huma Khan and Sunlen Miller contributed to this report.