Locating the Homeland

A Frenchman, an Italian, and a Bulgarian are on a trans-continental flight over Europe.

"Aha!" exclaims the Frenchman. "We're over my homeland of France right now!" The other two ask him how he knows. "If you do some simple math, it's easy to figure out." A while passes. "Aha!" exclaims the Italian. "NOW we're approaching my hometown." When asked how he knows, he says, "I know those mountains down there like the back of my hand!" Some more time goes by, and the Bulgarian shouts, "Aha! We just passed the neighborhood where I live." "How could you possibly know that?" the others ask. "Well, someone just stole my watch."