Think the jet in the picture above looks pretty close? That's because it is. In fact, it's twice as close as it could get to you prior to 2005.

So what's up with the close flybys these days? It's not just for good photo ops, it's actually because of something called 'RVSM', or Reduced Vertical Separation Minimum.

What is RVSM?

RVSM reduces the vertical separation of aircraft from 2,000 feet to 1,000 feet when they're flying at altitudes from FL290 (29,000 feet) to FL410 (41,000 feet).

So why is this happening? It significantly increases (in theory, it nearly doubles) the number of airplanes that can fly in a defined area of airspace. Plus, it allows pilots to pick more efficient altitudes and avoid turbulence.

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Flying Before RVSM

In the past, aircraft flying between the surface and FL290 needed 1,000 feet of vertical separation, but anyone flying above FL290 needed 2,000 feet of separation. The reason was simple: the accuracy of pressure altimeters decreases the higher you go, and at the time, altimeters weren't accurate enough to guarantee adequate separation between converging traffic.

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Modern Separation And Requirements

Modern aircraft are much better at accurately determining altitudes, and staying at their assigned altitudes with autopilots. Between the invention of Air Data Computers (ADCs), more accurate altimeters and advanced autopilots, the 2,000 foot separation rule is no longer as much of a concern, and that's what sparked the idea behind RVSM.

In 2005, RVSM was implemented from FL290 to FL410 in the lower 48 states, Alaska, the Gulf of Mexico, the Atlantic High Offshore Airspace, and the San Juan FIR.

Now pilots can fly at more efficient altitudes with 1,000 feet of separation, and Air Traffic Controllers to fit more jets into the sky. On top of that, jets are saving fuel by flying at more efficient altitudes. According to an FAA study as RVSM was rolled out, RVSM airline flights burned approximately 2.5% less fuel per trip on the 12 city-pairs that were studied.

More Equipment And Training Requirements

But with everything in aviation, there are rules that need to be followed. Aircraft flying in RVSM airspace need specially certified autopilots and altimeters, and pilots flying in RVSM airspace need specialized training (more on all of that here.) If you're not authorized to fly in RVSM airspace, ATC needs to keep you below FL290, or have you climb above FL410 (outside RVSM airspace) while staying at least 2,000 feet vertically from all other aircraft.

What It All Means For You

So what does this all mean for you? If you're flying below FL290, not a lot. But the next time you book an airline flight, you'll know your pilots can fly at more efficient altitudes, get you out of turbulence more easily, and give you the chance to snap some photos like these.

Live from the Flight Deck

Live from the Flight Deck

Live from the Flight Deck