In the past there has been no missile fast enough to shoot down our SR-71 spy planes.
The missiles could not catch them, isn't that a hoot? You fly by, capture all the footage and leave faster than their faster missiles; Pretty cool, right? Sure it was but then came spy satellites with very good and robust geospatial capabilities and you have heard the stories of being able to read a license plate from outer space.
The problem with many satellites is that there is times when the satellites are not over the area of interest.
Indeed those stationary geo-sync satellites are too high up to get a high resolutions you need from above and then there is weather too.
High speed and/or high altitude UAV Unmanned Aerial Vehicles are now being used for aerial surveillance.
And our current enemy, a few wannabe miscellaneous remaining international terrorist insurgents do not have the capacity to shoot them down.
Using small arms fire will not work and is liable to get them found out and then taken out upon giving away their position.
The answer for shooting down a fast moving UAV, spy plane, aircraft or ICBM will have to be high-energy directed laser beam.
Our future enemy will surely be more advanced than that of the cakewalk enemy we are now kicking the ever-living crap out of.
The Osama bin Laden wannabe followers.
Think on this.