Air-traffic controllers across the US will receive new monthly safety training sessions to address the spike in serious near-collisions on airport runways earlier this year. 

The Federal Aviation Administration is conducting the mandatory training starting in July, the agency said in a press release. The National Air Traffic Controllers Association union is collaborating with the effort, the FAA said Wednesday. 

There were eight incidents involving airliners on or near runways in January or February ranked by FAA as a serious risk of a collision or that prompted the National Transportation Safety Board to open an investigation. That’s almost double the annual average for the previous five years. 

“To reach our goal of zero close calls, everyone must stay sharp,” Tim Arel, the FAA Air Traffic Organization’s chief operating officer, said in the release. “This training will give us an opportunity to focus on safety with our entire workforce.” 

While there were no obvious common causes in the serious incidents this year, half of them involved errors by controllers, according to FAA data. The most serious incident occurred on Feb. 4 when a FedEx Corp. wide-body cargo jet attempting to land in Austin, Texas, came within 100 feet of colliding with a Southwest Airlines Co. plane cleared for takeoff on the same runway by a controller. 

The FAA had 10,578 fully certified controllers with about 3,000 more in various stages of training as of Sept. 30, the lowest it has been since at least 2000, according to an agency report to Congress. 

Since the spike in incidents, the FAA hosted a safety summit, created an independent team to review the issue and ordered supervisors to monitor air-traffic operations during peak periods, among other actions.