Planes flew too close to each other 4,394 times last year — more than doubling the previous record from 2011, the Federal Aviation Administration announced Thursday.
But in a new report, the agency drew no conclusions about whether skies are less safe because the incidents grew from greater voluntary reporting by air-traffic controllers and better radar detection that was fully deployed last year.
None of the incidents resulted in a collision. More than 99% of the country's nearly 133 million landings and takeoffs went off without a hitch.
"We run the safest and most efficient system in the world, and we have the most highly skilled controllers and technicians," David Grizzle, FAA's chief operating officer, said in a letter accompanying the report. "We've gone from counting errors to identifying and mitigating safety risk."
A spokesman for the National Air Traffic Controllers Association said his organization takes pride in the efforts to reduce safety incidents and increase reporting between controllers and the FAA.
"Safety is and always has been NATCA's top priority," said spokesman Doug Church. "The fact is they have made a difference and improved the overall safety of the aviation system."
Capt. Sean Cassidy, first vice president of the Air Line Pilots Association, a union representing 50,000 pilots, commended the FAA for refining how the agency is identifying risks and fixing risks.
"It doesn't make me worried about the level of safety because all we're doing is applying a more refined data-gathering measure," Cassidy said. "It increases the level of safety actually because it gives us a much more precise picture of what the world is like out there."
The numbers spiked because of better reporting of the incidents when planes were within 3 miles of each other horizontally when near an airport.
The FAA counted 1,895 incidents in 2011 where planes flew too close together or violated other air-traffic guidelines. That was just eight more than the year before.
Those numbers jumped significantly from the 1,234 incidents in 2009. That increase coincided with different reporting rules that encouraged air-traffic controllers to voluntarily report incidents without fear of reprisals.
In January 2012, a radar program was fully deployed to 189 sites nationwide to automatically detect when planes get too close. The program increased the amount of data that FAA collects by 10 times.The agency's goal is to study the problems reported by controllers or detected by machines and fix them before there's an accident.
Of the 4,394 incidents, the FAA focused on 1,271 where planes were at least one-third closer than regulations allow, or typically within 2 miles of each other horizontally near an airport.
The agency found 41 incidents characterized as "high-risk" under the new reporting system. The agency broke down the high-risk incidents into five categories: turns on final approach, using parallel runways, aborted landings called "go-arounds," flying mistakenly at the wrong altitude and faulty coordination between planes.
"Correction is the ultimate measure of our progress," Grizzle said.
Cassidy said pilots would monitor how FAA uses the information to remedy problems. And he said the key is to use the reporting to fix problems rather than as discipline for pilots or controllers who make honest mistakes.
"I'm fairly confident they are moving in the right direction and towards identifying these separation issues," Cassidy said.
The agency took 19 actions in 2012 to avoid the problems, according to the report.
For example, in dealing with parallel runways that are common at all of the country's largest airports, the agency found that as two planes approached the runways to land, one might turn too wide and blunder too close to the other plane. The remedy was to instruct pilots to turn sharper so they remained lined up with their own runway.