I have experienced this before even over the atlantic. Never got to the bottom of what causes it. Cleaned all my ai out and re-installed but the same thing happens. Very rare though. Funny seeing a turboprop trying to cross the pond!!I have mapped numeric keys in FSUIPC to control my traffic levels from 0% to 100%. In this instance i would normally just hit ctrl & num2 to reduce traffic levels to 20%. This allows the CPU to recover quickly. When the traffic has dispersed i upped the level again..Ian