According to the F.A.I. World record list;
http://records.fai.org/models/current.asp (Scroll about 2/3rds down)
A new straight-line speed record was established this year by
David Dzida of Germany with an electric-powered model airplane. The old record, from 1992, was 282.60 kilometers per hour (
175.59 mph).
The new record is 361 kilometers per hour, or
224.314 miles per hour, if my online converter is correct;
http://www.plasma.com/classroom/converterspeed.htm
It is also interesting that this new record is faster than the existing piston-powered straight-line record, 343.82 kilometers per hour (
213.639 mph), which dates from 1971.
Even faster are the turbine-powered models and the 301 mph (unofficial) dynamic soaring glider record.
http://www.wattflyer.com/forums/showthread.php?t=7567
Lots of other records on the F.A.I. site!
Ron