The jet stream over the Atlantic so strong that flights heading from the US to Europe are reaching speeds equivalent to that of sound. Passenger aircraft traveling east from the US across the Atlantic have reached up to 778 MPH. That's a little over 200 miles per hour faster than normal cruising speeds. How are these flights able to fly at the speed of sound? Specifically, accurately explain: What does it mean "reaching speeds equivalent to that of sound"? What does it mean "reached up to 778 MPIP"?