An interesting report about a B757 landing Accident at AMS in 1997.
http://www.nlr-atsi.com/downloads/rvtv-980861015.pdf
A short quote from the 'recommendations'
Aircraft manufacturers give limits for the maximum crosswind for each type of aircraft. They include a limit based on tests, the demonstrated crosswind, and a limit based on simulations, the manufacturer’s limit. In the case of the Boeing 757, the manufacturer’s limit is a crosswind of 40 knots (at an angle of 90° to the flight direction) and the demonstrated crosswind limit is, without gusts, 30 knots (also at 90°). The latter limit is generally adopted by aircraft users. In the case of Transavia, a note was included in the pilots’ manual, though a great deal was left to the judgement of the pilots themselves:
“X-wind (crosswind) > …” means that the given component is the maximum demonstrated crosswind during aeroplane type certification; this value is formally not limiting; however actual crosswind-components approaching (or even exceeding) these values should be treated as a strong incentive to divert to a runway with less crosswind.’
Regards, MAX