Can You Pass the Nearly Impossible Test Air Traffic Controllers Used to Take?

This simple-sounding numbers game is way harder than it looks.

Imagine 50 lines of numbers with 29 digits in each line. A number is circled at the beginning of each line, and your only task is to cross out all the numbers in that line that are identical to the one in the circle.

Sounds simple, right? You’d get a bit bored, but you’d probably pass.

Now try adding a 2 ½-minute time limit. If you think the task will remain easy as pie, you’re wrong. By 1961 at least, after hundreds of attempts, no one had been able to complete it, according to the September issue of that year’s Reader’s Digest. Make sure you do know the 13 things airlines don’t want to tell you.

The quiz in question was developed to test perceptional speed in aspiring air traffic controllers. “The aim here is to test recognition of a known object embedded in a number of irrelevant objects,” James H. Winchester wrote in his 1961 article, which appeared in the journal Air Facts before it was condensed for the Digest. “This is vital to an airport tower operator, who has to pick out the one object he is controlling form among a myriad of blips on a scrambled radarscope, or recognize one airplane over another in a fleeting flash in a busy sky.” Here are the meanings behind these 11 mysterious flight codes.

The time limit on the probe wasn’t the only challenge—students were also mentally fatigued by the time they got to it. “Forty-four oral and written tests are administered in a continuous eight-hour stretch,” Winchester wrote. “These tests determine reaction time, memory, retention of information, coordination, mathematical competence and perception. The hardest papers are reserved for late in the day, when students are mentally fatigued.”

Other brain-busting tests included a speed-of-closure probe in which candidates were asked to find four-letter words in a jumble of letters. For example, in the line…


…the words are “poet,” “moss,” “auto,” and “many.”

A third probe tested delayed memory: An instructor would read a story and quiz the candidate on two entirely unrelated tasks for five minutes. When the five minutes were up, the students would be asked to answer questions about the story, thus proving their ability to absorb information, switch their focus, and recall the original task. Learn these science-backed ways for surviving a plane crash.

Still think you’ve got what it takes?

“It’s a stress job,” said Bill Berkeley, an instructor at the Federal Aviation Agency’s training center in Oklahoma City at the time. “We get a student up to a point where he thinks he can’t take it any more, and then we throw him another puzzle, to judge his ability to respond.”