Just a short review about this program to note it's probably not what you expect. When I watched it last night, it was paired (in ads) with When Aliens Attack (largely a wargame scenario, positing a long campaign against an invading force). From that juxtaposition, you might thing this would be another "aliens hidden in Area 51" program. It's not.
Instead, it's a serious look at what really went on in Area 51 in the 50s and 60s (largely), during the testing and development of the U2, SR-71, and other top-secret airplanes and projects. The interviewees tell their stories in a way that will be familiar to anyone who's ever watched a History Channel war program -- that is to say with candor, humor, and professionalism. My favorite moment was when they discovered that a Soviet satellite had seen the shape of a top-secret plane on the runway; the enemy knew what our best plane looked like! To counter this, the Area 51 crew started making cardboard silhouettes of fake aircraft for the satellite to "find." They even put heaters on the cut-outs to simulate cooling engines. Great deception.
No aliens here, just good, old spy vs. spy Cold War era politics. Highly entertaining and informative.