Helicopters are a marvel of modern aviation technology, but given that the rotor blades are doing all of the heavy work, what are they made of?

How helicopter may have crashed in Hudson River. FOX 5 NY's Linda Schmidt is live on the scene after a helicopter crashed into the Hudson River.

The April 10 crash in the Hudson River killed six, including a Spanish couple who worked for manufacturing conglomerate Siemens, the couple’s three children and the helicopter pilot.

The helicopter tourism industry sends some 30,000 flights over the Big Apple every year. Other tragic crashes have prompted regulations. But even a successful flight can be controversial.

The Brief. Six people died when a helicopter crashed into the Hudson River Thursday afternoon. One aviation expert says that the entire rotor assembly may have come off, causing the crash.