In a couple of WWII documentaries that I've watched recently, I've noticed that Winston Churchill visited Moscow and Cairo both in 1942, when the tides hasn't turned yet in favor of Allies. How was this possible? I can understand that it was rather safe to use a sea route to Cairo, making a stop in Malta or Gibraltar (even though, wasn't there Italian navy?), but a voyage to Moscow meant the usage of air transport, and the German occupied airspace. These are the dangerous examples I can think of, I'm sure there must be plenty of more.