separation in the skies breached. the faa's latest numbers show planes came too close nearly 4400 times in one year. 41 of them deemed high-risk events. >> they are scary and unacceptable but there's a back-up system and people are safe. >> reporter: it's an air traffic system under stress. increasing air traffic and a potential shortage of controllers. almost thousands need to be hired and trained over the next seven years. some experts worry the agency's new hiring practices could make matters worse. the agency no longer gives preference to recent graduates from aviation colleges. just last month, a government auditor said he would study controller staffing levels and the impact of retirement. but incidents where planes get too close are not necessarily controller mistakes. >> this could occur through a controller making an error,