Flying the Fastest Skies

February 20, 2019 · 0 comments

How fast can an airliner go? Monday night a Virgin Atlantic Boeing 787-9 reached 801 m.p.h. en route from Los Angeles to London. Matthew Cappucci of the Washington Post reported the jet reached this amazing speed—a record for the Boeing 787-9 and probably the highest speed for a non-supersonic commercial flight—while cruising at 35,000 feet over the central Pennsylvania.

Clearly the plane was hurled along by an intense jet streak; Cappucci showed a sounding at 250 mb—a level nearly as high as the plane—that night over Long Island: the jet stream was moving at 231 m.p.h. This is what pushed the aircraft more than 200 m.p.h. beyond its top airspeed. (The plane’s record speed was relative to the ground, not the swiftly moving air around it.) The Post article states that the sounding “sets the record for the fastest 250-millibar wind speed ever recorded over New York and, probably, the country.”

This raises the other question of speed: just how fast can a jet stream go? It turns out the question is not so easy to answer. To find out, we e-mailed an experienced weather records sleuth, Arizona State University’s Randy Cerveny, who is the World Meteorological Organization’s rapporteur of weather and climate extremes. Cerveny replied,

I had set up a WMO committee this past summer to look into that very question—the strongest tropospheric winds (and so the strongest winds recorded on the planet). As we started to look at the data, we found that by far the strongest tropospheric winds are found east of Japan in the Pacific and normally occur right at this time of the year. They are associated with the normal area when polar and subtropical jets merge. The second area of max tropospheric winds are over New Hampshire and has the same thing happen—polar and subtropical jets merge. BUT unfortunately we ran into serious problems with the quality of extreme tropospheric wind measurements. My experts say that right now the quality of the data for those upper air extreme winds is not good enough to support an investigation for global fastest tropospheric winds. So we are not investigating that record until (and if) NCEI and other groups can establish a viable record for an extreme. We have seen data (again, not good to accept) that has winds in excess of 133 m/s or 297 miles per hour. It is likely that some of those values ARE good but we are still quality-controlling the radiosonde extreme dataset.

With that in mind, we dug into the AMS journals archive and found a February 1955 Journal of Meteorology article by Herbert Riehl, F. A. Berry, and H. Maynard detailing research flights into the jet stream over the Mid-Atlantic states. They record one case of a 240-knot jet stream (276 m.p.h.) and another of 210 knots (241 m.p.h.), each representing averages over 28 miles of flight path.

These can’t be counted as definitive—Riehl et al. emphasized the difficulties of their measurement process. And Cerveny emphasizes that, “No measurement that we have seen at extreme values has been judged of sufficient quality to warrant a full evaluation at this time.”

So for now, just sit back and enjoy the flight.