U.S. airplane near collisons doubled last year

The number of times U.S. airplanes nearly collided more than doubled last year, though the biggest increase by far was in the low-risk category, a new Federal Aviation Administration report said.

Last year there also were 224 medium-risk near-misses, up 23 percent from 182 in 2012, the FAA report says. Meanwhile, the low-risk category leaped 100 percent, rising to 2,097 from 1,048. However, these spikes might simply reflect a leap in reporting.

The FAA technically calls near misses a "loss of separation." The top safety threat it identified revolves around communications, which impeded recoveries after planes nearly collided. The other top hazards were not issuing advisories, faulty monitoring, overly similar sounding call signs, and conflicting procedures.