[Raebie]

I thought it was 80%, but either way, you're looking at 68-70 MPH winds.

[nwctwx]

Based on this new understanding, NOAA’s National Hurricane Center typically now uses a factor of 90 percent to estimate a hurricane’s maximum surface winds from flight-level observations. This means that the winds of some storms in the historical record may have been underestimated.

http://www.noaanews.noaa.gov/stories/s966b.htm