ALPENA — The Alpena Combat Readiness Training Center (CRTC) verified in a statement on Facebook around 2 p.m. on Tuesday that the loud booms heard in and around Alpena were in fact sonic booms. “Your local Airmen are training to stay mission-ready,” the CRTC posted on Facebook, then thanked the community for their support and understanding. “Military training flights over northern Michigan sometimes require supersonic speeds, leading to occasional sonic booms,” the CRTC post stated. “These occur in designated high-altitude airspace to ensure safety while preparing our ...