An airport control tower is seen at Newark Liberty International Airport, on May 6, 2025 in Newark, New Jersey. Andres Kudacki | Getty ImagesAir traffic controllers have been under strain for years, but a 90-second equipment failure last month exposed how decades of staffing shortages, underinvestment and patchwork solutions for those who guide planes through some of the world's most congested airspace are taking their toll.The outage also sparked hundreds of flight delays, disrupting travel for thousands of people for days — again. Less than two weeks later, on...