A Qatar Airways Boeing 777, like the one pictured above, reached a top ground speed of 833 mph.Nicolas Economou/SOPA Images/LightRocket/GettyOn Wednesday, at least two transatlantic flights reached top ground speeds above 800 mph.They were still technically subsonic because they were propelled by a faster-than-usual jet stream.Recent cold weather strengthened the jet stream, and the climate crisis is set to exacerbate this.Some transatlantic flights traveled faster than the speed of sound relative to the ground this week.It isn't the return of Concorde — instead, regular wide-body jets were flying through an accelerated jet stream.According to data from Flightradar24, Qatar Airways Flight 704 reached a top ground speed of 833 mph as it crossed the Atlantic on Wednesday.The Boeing 777 flying from New York to Doha landed about 50 minutes ahead of schedule.Also briefly traveling above the speed of sound was British Airways Flight 274, which hit a top ground speed of 814 mph during a trip to London from Las Vegas, per Flightradar24 data.The Airbus A350 landed 45 minutes ahead of schedule.While both flights' top speeds were above Mach 1.2 when taking their cruising altitudes into account, there would not have been a sonic boom.The planes were traveling at their usual cruising speeds — typically about 600 mph — but were propelled by the North Atlantic jet stream flowing much faster than usual.So, while the planes traveled above the speed of sound relative to the ground, they were still subsonic relative to the air around them.The jet stream has been made more powerful than usual by the recent cold spell in the US.This was also set to bring high winds to the UK and Ireland as part of Storm Éowyn.