In Chapter 368 of Dragon Ball, Bulma finishes a remote to detonate the androids. Pages later, in Chapter 369, Master Roshi says she's 20 minutes away from Kame House. Krillin says that if he goes all out he'll be faster than her plane, giving us a good statement to scale his speed off of.
Keep in mind, this is a low ball. We don't know how long Bulma was flying before the 20 minute statement (though I doubt it was more than five or so minutes, just based on context), and Krillin's speed slightly surpasses the plane's, it doesn't match it. This isn't a figure on what Krillin's top speed is during the Imperfect Cell Saga, more something showing what ballpark it should be in.
With that in mind, we're going to measure this like we have our previous flight calculations. One using the "Goku's house" statement, one assuming the planet is the same size as our own.
The distance between Kame House and Capsule Corp is about 260 "units". Comparing this to the planet's radius, assuming that equals our own, puts a distance of around 16,500 km between Kame House and Capsule Corp. Comparing that to the distance between Satan City and Goku's house, which are 40 "units" and 1000 km apart, would bump this down to 6500 km.
v = d/t
- d = 16,500,000 m
- t = 1200 s
16,500,000/1200 = 13,750 m/s, which we'll round to 13,800 m/s
v = d/t
- d = 6,500,000 m
- t = 1200 s
6,500,000/1200 = 5420 m/s
Results
- Krillin Outspeeds a Plane ("Our World" Method) - Mach 40.6, Hypersonic Class
- Krillin Outspeeds a Plane ("Goku's House" Method) - Mach 15.9, Hypersonic Class