From Business Insider by Brad Howard:
Since the United States entered World War II, the Department of Defense has engaged in the systematic surveillance of other nations by air to glean valuable intelligence on weapons capabilities and military movements. These missions are quite dangerous and often ended in disaster, but the risks endured by these aircrews aboard the Pentagon’s beloved spy planes are often overlooked due to the sensitive nature of their assignments.
Here are five instances from the past that illustrate why these pilots were not flying the friendly skies:
1. A tense shoot-down over the Baltic Sea:
As the Iron Curtain descended across Europe, the United States was desperately trying to gather intelligence on Soviet activities across the continent.
On April 8th, 1950, a PB4Y-2 Privateer — a modified B-24 Liberator fitted with electronic gear for signals intelligence — left West Germany for the Baltic Sea to gather intel on Soviet naval forces and possibly to monitor early naval missile tests.