I could go into a physics based answer, but I'll chose a more down to Earth approach.
The maximum airspeed of a 747 is somewhere around Mach 0.92 or 1,100km/hr (705 miles per hour). Your cruise speed is around 920km/hr (570 mph) (https://en.wikipedia.org/wiki/Boeing_747).
Your category five cyclone comes in at usually just over 251 km/hr (74 miles per hour) (https://en.wikipedia.org/wiki/Tropical_cyclone_scales). Even multiplying this by four, it still just compares to the awesome speed of a 747. And even still, the maximum airspeed of a 747 is still only a few hundred km/hr above what the cruising speed is. The fortification to increase this would add weight, and reduce this further.
So for a practical answer, the max speed you could add is the maximum airspeed less your standard cruising speed, plus maybe 60mph for "science fiction" added fortifications increasing max airspeed. The reason why I haven't just added your cyclone speed to your cruising speed, is if you were to suddenly exit the jetstream, you could now be over speed (although this value is still coincidentally similar to the speed of a category 5, so little risk there). So the |maximum| is somewhere around 280km/hr with minimal fuel cost assuming a massive high power category 5 cyclone.
However, you not only decrease safety, but the speed increase in reality is negligible for the fuel costs you may save (vs the price spent fortifying an aircraft). It wouldn't be unthinkable that this could actually decrease your aircraft speed.
The only benifit could be fuel costs, but those are negated by safety.
If this is science fiction, you could work in gliders that run on minimal power, and focus on the fuel saving aspect rather than the speed benefit aspect. We already have conventional aircraft that travel unimaginably fast, with very little risk.
Enter the "AirPlane". It's not for travel, but it builds a thriving tourism industry! How?
Use the cyclone to whisk people around in a dome, like a theme park ride. You're tethered to the ground, and it's perfectly "safe", and people pay tons for the experience of riding the cyclone. Then re-invest the money in super sea cruisers and non-cyclone based aircraft.