English is being used more and more as the international language of business. An example of that is the recent decision of the Milan Polythechnic to use it as their teaching medium. And ten years ago, English speakers were rare. Now you can find them everywhere. The increasing globalisation of business and industry requires a common communication medium, and those who can't use it will lose out.
In his book 'To rule the waves', Arthur Herman claims that it was on 15 July 1588 when events lead to English becoming the world's dominant language. The Royal Navy's final routing of the Spanish Armarda at the battle of Gravelines led to Spain's decline as the pricipal world power and the start of England's (later Britain's) dominance. Had the battle gone the other way, we would probably all be speaking Spanish on the airwaves!