U.S. Transportation Secretary Pete Buttigieg said Wednesday that the country’s air system was skirting disaster in the wake of multiple near-miss aviation incidents in the past year.

Speaking at an air safety summit convened by the Federal Aviation Administration, Buttigieg said that while the U.S. continues to enjoy “the safest and most complex system in the world,” there are indications that the system is under strain.

“We can’t wait for the next catastrophic event when we can see the warning signs today,” he said.

The summit comes amid a recent spate of runway incursions and other near disasters in the skies that have shaken the public.