What aviation incidents occurred in North America prior to the Delta Flight 4819 crash?

In the three weeks before the Delta Flight 4819 incident, North America experienced multiple fatal aviation accidents. First, 67 people died when an American Airlines jet collided with a Black Hawk helicopter near Washington DC's Ronald Reagan Airport. The helicopter was flying higher than authorized. Just two days after that collision, a medical jet crashed in Philadelphia shortly after takeoff, killing all six people aboard and one person on the ground. This series of tragic incidents has significantly alarmed the North American aviation industry, raising serious safety concerns.