Official gives update on recovery efforts; president weighs in on cause of collision in highly unusual move as investigation still under way

• Alarms raised about ‘congested’ airspace before fatal Washington crash
• Staffing levels ‘not normal’ in control tower at time of crash, report says

Reagan national’s main runway is the busiest in the United States, with more than 800 daily takeoffs and landings.

The National Transportation Safety Board has investigated nine accidents or incidents at the airport this century, including two that were fatal, records showed.