High Alert: US Flies B-1B Over South in Show of Force Against N. Korea. The United States flew a B-1B supersonic bomber over South Korea on Wednesday as part of a massive combined aerial exercise involving hundreds of warplanes, a clear warning after North Korea last week tested its biggest and most powerful missile yet. B-1Bs flyovers have become an increasingly familiar show of force to North Korea, which after three intercontinental ballistic missile tests has clearly moved closer toward building a nuclear arsenal that could viably target the U.S. mainland.