More close calls over the nation's skies are getting reported than ever before.

FOX News Radio's Jill Nado reports:

Nearly 4,400 incidents reported in 2012 of planes getting too close to each other in U.S. air space. And that number is nearly double what we saw in 2011. It's not that pilots are getting sloppy, it's because there's now better data collection about incidents like these. And how close is too close? The FAA says it's 3.5 miles and Captain Sean Cassidy of the Air Line Pilots Association says that may seem like a long distance, but...

(Cassidy) "It's better to be conservative and get more of these things reported so that we can troubleshoot and see where the risk factors are."

And the FAA says 99% of all take offs and landings in the U.S. were trouble free.

In Washington, Jill Nado, FOX News Radio.