It's extraordinary how fast you can go â. - former pilot Alastair Rosenschein. Eastbound flights often have up to an hour clipped by the jetstream, which is usually at a similar altitude to that of a cruising plane, but pilots must be skilled to ride them as they are usually 10 miles across and 2,000 feet in depth.t's extraordinary how fast you can go â. - former pilot Alastair Rosenschein. Eastbound flights often have up to an hour clipped by the jetstream, which is usually at a similar altitude to that of a cruising plane, but pilots must be skilled to ride them as they are usually 10 miles across and 2,000 feet in depth.