Classify the following as either airplanes or helicopters:
- EC-135
- DC-10
- Antonov An 225
- Boeing 787
- Bell 206
- MD-500
- MD-11
- Airbus A320
- Airbus H165
- Cessna 172

Airplanes:
- McDonnell Douglas DC-10
- Antonov An-225
- Boeing 787
- MD-11
- Airbus A320
- Cessna 172

Helicopters:
- Bell 206
- Robinson R44
- MD-500
- Airbus H165