HELP NEEDED! - The Convair 990A was the fastest subsonic airliner ever... or was it?

Real World Aviation
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Yesterday I caught myself watching a bunch of videos from a famous YouTube channel on aviation failures. Eventually, I landed on his Convair 990 video, which, as many others, claims the aircraft was the fastest subsonic airliner ever.

Naturally, the question arises: by what metric, and, especially, by how much? First, I tried the obvious: Wikipedia. While it’s generally a great website to get airplane specs from, it wasn’t exactly helpful in this case, even contradicting itself, with the spec sheet provided in the article claiming a maximum speed of M0.871, and a maximum dive speed of M0.91, while simultaneously claiming Convair was successfully able to achieve M0.89 (presumably in level flight) as requested by American Airlines. It also claims a cruise speed of M0.84.

So, I decied to dig a little deeper. What I found was that it’s actually not so easy to find Mach numbers for the 990/990A, and, on the websites that do have it, they’re all over the place. One website I found claims the cruise speed of the 990 is M0.87 and the maximum speed is M0.91, putting the aircraft as the fastest in terms of typical cruise speed. However, another website claims the numbers are, respectively, M0.84 and M0.89, ridiculously low figures for what’s claimed to be the fastest subsonic airliner of all time.

For comparison sake, the Boeing 747-400, the fastest airliner currently in operation has a typical cruise speed of M0.855, according to a Boeing document, and a maximum speed of M0.92, according to this FAA document. Some may claim the 747-8 is faster, however Boeing advertises the same typical cruising speed, and it’s certified for a slightly slower maximum of M0.9.

If anyone can find a definitive answer on the typical and maximum Mach speeds of the CV-990/990A, I’ll be very thankful. Perhaps we’ll be able to figure out whether the CV-990A still holds the record, or if it’s one of the biggest pieces of misinformation spread in aviation, having been true during its time in the 1960s, but having long been beaten by the Queen of the Skies.

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It sounds like it hit the target speed of 635 mph. A Reddit post I read said it reached Mach 0.97. No information backing it up though

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From the Wikipedia article, that was apparently during a dive. If dives count, then maybe we should consider the DC-8 to be the fastest, as it went supersonic despite not being designed to do so?

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Let’s put it this way: American Airlines wanted a jet to be at least 45 minutes faster than other jets when traveling from east to west. The ground speed needed to be at least 635 mph. If we take into consideration the altitude (let’s say 30,000 feet with the standard characteristics of temperature and air pressure), the head winds commonly associated with flying west (let’s just say a 80 knot head wind), the aircraft’s TAS would need to be around 725 mph or Mach 0.95 to maintain 635 mph ground speed.

Just some rough calculations I got out of ChatGPT

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So I guess on paper the aircraft needed to be able to cruise at Mach 0.95. The 0.97 is probably the maximum structural speed it could reach