What are typical causes of major speed spike during a flight?

Quick question from a person with a limited knowledge of flying in the cockpit:

While checking FlightAware site for yesterday's Condor flight PHX-FRA, I noticed a significant spike in speed about halfway through the flight, lasting for a total of 3 minutes. The surge in speed happened just about when the flight was leaving Canadian coast line and starting over the Atlantic. The altitude did not change, and it remained constant, as filed, for the duration of the flight. Here is my question for the experts: what could have caused a brief but sudden doubling of speed mid-flight?

Here is some additional info, if it helps to answer my question:



Date: May 18

Flight: Condor 2027, PHX-FRA

Equipment: A 330-900

Filed Altitude: 37,000 ft (remained pretty constant )

Filed speed: 545 mph ( maintained for most of the flight )

Speed spike: from 575 mph to 1018 mph ( lasting less than 3 minutes )

Was it something normal? Does it happen often? Is it a mistake on FlightAware?

Penny for your thoughts.