Are you going by plane?
Yes, I am.
Are you going by car?
No, I'm not. I'm going by hot-air balloon.
Are you going by taxi?
Yes, I am.
Are you going by plane?
No,I'm not. I'm going by train?
Are they going by bus?
No, they aren't. They are going by truck.
Are you going on foot?
No, I'm not. I'm going by helicopter.
Are you going by motorcycle?
Yes, I am.
Are they going on foot?
Yes, they are.
Are they going by tandem?
Yes, they are.
Are they going by boat?
Yes, they are.