In my region of the country, class G airspace doesn't go higher than 1200 feet AGL. (Close to airports with instrument approaches, it is 700 or zero.) However, in some parts of the country, some class G goes up to 14,500 msl. Why is this airspace class G instead of class E? The rules for operating VFR above 1200 feet in that airspace are almost identical to the rules for operating in class E airspace. (The only difference seems to be the visibility requirement during the day below 10,000 feet MSL is reduced.) Having this airspace be class G just makes the rules unduly complicated without a practical difference. Am I missing something?
Class G above 1200 feet AGL
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I think it would generally be very remote areas without radar or comms reception, hence uncontrolled airspace, or class G. Can't make it class E/controlled if we have no way of controlling the airspace.
There are differences for VFR visibility/cloud clearance.
The big difference comes for IFR operations. You are required and can receive clearances in controlled airspace (class E or above). You can't in class G.
The big difference comes for IFR operations. You are required and can receive clearances in controlled airspace (class E or above). You can't in class G.
Larry in TN
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In the beginning, all airspace was G (even though the name came much later). Airspace was upgraded from G to higher classes as it was needed to facilitate IFR flight.
As RADAR coverage expanded, making low-altitude IFR practical outside of airways, the floor of controlled airspace was lowered to give ATC authority to control IFR aircraft in those areas.
The increased visibility and cloud clearance requirements of controlled airspace are to allow VFR aircraft time to see-and-avoid IFR aircraft which can operate without any visibility.
As RADAR coverage expanded, making low-altitude IFR practical outside of airways, the floor of controlled airspace was lowered to give ATC authority to control IFR aircraft in those areas.
The increased visibility and cloud clearance requirements of controlled airspace are to allow VFR aircraft time to see-and-avoid IFR aircraft which can operate without any visibility.
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Vintage Snazzy (so my adult children say)
It's not like you've got 13,000 feet of class G. If G goes to 14,500 feet it's because the ground underneath is very high start with.
G floor is determined by its MSL. Class E floor is determined by AGL (mostly). In most places E's floor is 1200 feet above G. (E can also start at 700 AGL in areas of the country. It can also skip "sitting on top of G" altogether if depicted in the sectional chart as starting on ground level).
Example: If a patch of ground is at 13,000 MSL, E will start at 1200 AGL from that, or 14,200. So even though G goes to 14,200, it's not as if you have over 10,000 feet of G airspace underneath you. You’ll have the same amount of G as anywhere else.
G floor is determined by its MSL. Class E floor is determined by AGL (mostly). In most places E's floor is 1200 feet above G. (E can also start at 700 AGL in areas of the country. It can also skip "sitting on top of G" altogether if depicted in the sectional chart as starting on ground level).
Example: If a patch of ground is at 13,000 MSL, E will start at 1200 AGL from that, or 14,200. So even though G goes to 14,200, it's not as if you have over 10,000 feet of G airspace underneath you. You’ll have the same amount of G as anywhere else.
Sectional and other charts depict all locations of Class E airspace with bases below 14,500 feet MSL. In areas where charts do not depict a class E base, class E begins at 14,500 feet MSL.
Class G Airspace
Uncontrolled airspace or Class G airspace is the portion of the airspace that has not been designated as Class A, B, C,D, or E. It is therefore designated uncontrolled airspace. Class G airspace extends from the surface to the base of the overlying Class E airspace.
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I believe that would be an accurate statement for the CONUS now, but that hasn't always been the case and it appears that there are still a few places in Alaska where you might have 10,000' of class G airspace. Things changed when ADSB became commonplace and the majority of aircraft were transmitting their position and altitude rather than solely relying on radar to "see" the aircraft.
Larry in TN
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I've flown a DC8 IFR into an airport around which the floor of controlled airspace was FL245.
As you imply, there used to be a lot of Glass G below 14,500' in the western US. Someone learning to fly today would have no idea that it ever existed.
RussR
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Look at the Big Bend area of Texas, say, West of 6R6. There's 14500 Class G down there.
There's another block in Western NM. Maybe a few others.
There used to be much more, and this Class G airspace was very much NOT just in areas of high terrain. In fact, up until just recently, I'd say maybe 5 years ago, but certainly not more than 10, there was a pretty easily definable line roughly from North Dakota south southwest towards NM where West of that line there was quite a bit of 14500 Class G airspace (and obviously ND, etc., are not high terrain).
In that case, then why are the visibility and cloud clearance requirements in this type of class G airspace almost the same as they are in class E airspace? The only difference is the visibility during the day below 10,000 MSL. (reference: Table 3-1-1 in Chapter 3 of the FAR/AIM)
It was my understanding that the cloud clearance requirements were based on the scenario of an IFR airplane popping out of a cloud. If a VFR aircraft is flying too close to that cloud, the two aircraft could be very close to one another before either had an opportunity to see the other. However, in this type of class G airspace, like other class G airspace, there shouldn't be aircraft popping out of clouds because there shouldn't be any in the clouds. So, below 10,000 feet, why should this "high" class G have more stringent rules than "regular" class G? I do understand why the rules change at 10,000 feet.
Larry in TN
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The Class G, between 1,200' AGL and 10,000' MSL have changed over the years. It didn't used to be as restrictive as it is today.
Nobody said there won't be IFR airplanes poking out of a cloud in Class G airspace, just that ATC doesn't have authority over them. As I said, I flew DCs into an airport that had Class G from the surface up to FL245. We fly IFR through clouds in that airspace, we just didn't have an IFR clearance for it.
Is it possible to get an IFR clearance anywhere in class E airspace? I thought that there were minimum altitudes in different places below which a controller wouldn't give a clearance. Those minimum altitudes wouldn't be shown on the charts necessarily, but controllers would know them.
I am a VFR only pilot, so my knowledge of IFR flying is superficial. My understand was that IFR airplanes always needed a clearance from ATC. Am I mistaken about that?
If IFR airplanes can pop out of clouds in class G, then why are the cloud clearance rules relaxed?
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Vintage Snazzy (so my adult children say)
Yes - you have to get a clearance from ATC to fly IFR. Otherwise they aren’t working and talking with you / paying attention to you.
Why relaxed rules in “G”? IDK. Maybe less traffic in G, maybe it’s “you’re all on your own - good luck” airspace, etc.
Why relaxed rules in “G”? IDK. Maybe less traffic in G, maybe it’s “you’re all on your own - good luck” airspace, etc.
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Vintage Snazzy (so my adult children say)
My bad - not quite following. You usually get a clearance (activation) of your IFR plan on the ground. You can also call for an IFR plan and clearance when in the air for a “pop up”IFR flight plan. You’d do this for example when you’re flying VFR but clouds come in and you need to switch to instruments.
So yes - you can get an IFR clearance in E. You can fly IFR with your clearance in A,B,C,D,E, and G. You may not be able to be tracked in G so you make position reports when able and when required.
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Ari
You have to get an ATC clearance to fly IFR in controlled airspace. You don’t need a clearance to fly IFR in uncontrolled (Class G) airspace. It’s not a common event with the loss of almost all Class G airspace at altitudes where en route IFR is possible, but that’s a relatively recent development.
As far as why some Class G airspace goes as high as 14,500, it’s mostly because Class E (controlled) airspace isn’t designated there. Historically, I think that was due to the lack of ATC services that could be provided in such places. There were always bands of Class E designated for federal airways, along which the MEA would get you radio contact with ATC and navaid reception to stay on the airway. Hopefully someone can share a chart from maybe 10 or 20 years ago to show what that looked like.
Controlled airspace and the rules in it exist mostly to separate IFR traffic. Separation of VFR traffic is provided by the VFR pilots, and the restrictions on what you can do under VFR in a particular airspace are entirely to enable you to maintain separation from both VFR and IFR aircraft using your eyeballs.
The latest historical chart that I could find at the LOC was 1970.
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Vintage Snazzy (so my adult children say)
Trivia: “A” airspace ends at 60,000. Then it’s back to E. The ISS in orbit is in E. So now doesn’t it need an ADSB Out when it flies over the US? 
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Ari
That's perfect, thanks! The various Class E floors and relationships to airways are exactly what I was thinking of.
You can not get, nor do you need, a clearance to fly IFR in class G. Of course, given the damn little class G and most of it being below MIAs other than for takeoff and landing, you'd better have a clearance for the overlying controlled airspace before launching into IMC. The FAA has thrown 91.13 at people who've tried otherwise.
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Vintage Snazzy (so my adult children say)
Ah - I was answering the question “can you get IFR clearance in E”.
Now assuming you get a clearance in E, you can fly through E as well as other airspace categories.
If you fly into a G airspace along the way, I can’t say whether or not ATC would terminate you. I would think not, but it’s a good trivia question.
Now assuming you get a clearance in E, you can fly through E as well as other airspace categories.
If you fly into a G airspace along the way, I can’t say whether or not ATC would terminate you. I would think not, but it’s a good trivia question.
flyingcheesehead
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You can get a clearance, because it's pretty much a sure thing these days that you'll be in E sooner or later. The clearance might have something in it that sounds like "Upon entering controlled airspace, fly heading 120."
Theoretically, if you're in class G you can fly IFR without a clearance. That said, the FAA has all but eliminated class G above 1200 AGL in the US, so this remains pretty much a theoretical exercise these days. At the time I got my instrument rating, it was still possible to fly an entire flight in class G in some spots out west.
Thanks. I did not know that. I presume IFR flights are allowed to fly in the clouds in class G, like they do elsewhere? In that case, is separation between IFR flights in class G essentially based on the big sky theory?
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Vintage Snazzy (so my adult children say)
Had no idea how wide class G was back in the day. Given it was pre ADSB and GPS it must have been quite something.
The only IFR G I fly is the 700 feet from the ground to E that I’m in when taking off from my non towered field.
Larry in TN
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In the beginning, all airspace was what is now called Class G. Some airspace was later designated as Controlled Airspace in order to give ATC the authority to control IFR traffic in that airspace so that separation services could be provided. IFR separation won't work unless all airplanes are required to participate.
ATC clearance is only required to fly IFR in controlled airspace. That's why it's called "controlled" airspace.
Us civilian pilots typically learn to fly VFR first then IFR later. This often gives us a skewed view on the purpose of controlled airspace.
What is IFR, the Instrument Flight Rules?
They are listed in 91.167 through 91.199. (The Visual Flight Rules are 91.151 - 91.165)
Look through the instrument flight rules for the rule (91.173) which requires an ATC clearance and see to what it applies.
As the ATC system developed, controlled airspace was added around airports with extensions to protect approaches, and along airways. This was long before VORs. A/N ranges and NDBs were used to define, and navigate the airways and approaches. This system allowed an IFR flight to depart, climb, fly enroute, descend, fly an approach, and land in controlled airspace on an IFR clearance. At the time, pre-WWII, there wasn't RADAR. Everything was non-RADAR separation depending on position reports, airways, and enroute holding, to keep airplane separated.
Today's new instrument pilot in the US sees a system that appears to be based on RADAR. RADAR is just the shortcut that has been added on top of the existing system which was based on NAVAIDs and airways. Non-RADAR separation is rarely seen in the CONUS today, expect for departures and arrivals at remote airports without an approach control facility or in the overnight hours when it is closed. Most of the rest of the globe is non-RADAR, though, and non-RADAR separation is still used extensively. All of the flights from the northeast US to the Caribbean are non-RADAR, giving position reports to ARINC on HF (and transitioning to satellite CPDLC).
I mentioned flying DC8s into an airport where the floor of controlled airspace is FL245. That is Diego Garcia (FJDG) in the Indian Ocean. We'd be westbound from Singapore on UR212 with Brisbane Radio (non-RADAR). They'd descend us to FL240 reaching their western FIR boundary (GUDUG), 155NM from the airport, at which point they'd terminate us. We'd call Diego Tower, which provides IFR traffic advisories to participating aircraft (there usually aren't any others). They'd read us the weather and ask us what approach we were going to fly (no approach clearance since it's uncontrolled airspace). Based on the approach, they'd tell us a fix to report then clear us to land when we reported it. Departing would be similar. We'd get our oceanic clearance, starting at the FIR boundary, the depart. Diego Tower could send a departure message, with our departure time and estimate for the FIR boundary fix, to the next facility, Brisbane going east or Mumbai going north). We'd initially climb to FL240, to remain in the uncontrolled airspace, and would start trying to raise the next controlling agency on HF. When we established contact we'd request a climb after passing the FIR boundary.
For those interested in how the ATC (should) work, and any instrument rated pilot or student, I recommend the AvWeb Say Again? articles by Don Brown. There's a lot of good information in his articles for VFR pilots, too.
luvflyin
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Not having radar is distinct from being uncontrolled. The old controlled airspace (continental control area, control zones, transition areas, and victor airways) worked just fine without RADAR. Even today from time to time you get a case where the radar is out. I was heading down to Southport NC one day from DC and they say "we're going to have to put you back on an airway, Seymour johnson's radar is out). Got to give the old PTATEN reports. That's when I found out that it's really trivial on the GNS480 when you just expand the flight plan and it shows ETE to all the fixes ahead of you on the airway.
I know. The addition of that to my comment was primarily to describe the environment up there, not directly address the controlled vs. uncontrolled airspace part.
I’ve flown a number of instrument flights from start to finish in class G with no clearance and plenty of IMC, including approaches. And up until ADSB became common my usual instrument flying routes took me through airspace that had little or no radar coverage below 7,000’ AGL. It’s a different world that most pilots who have gotten an instrument rating recently would find hard to believe exists.
bluerooster
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shorty
But, On that chart there are no class A, B, C, D, E, or G airspace. But I do see uncontrolled airspace, controlled airspace, and ATA/CZ. (what it was in the '70s)
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Vintage Snazzy (so my adult children say)
Good trivia point. A B C D E and G is what, 10 years old?
BONUS Question: Why no “F”?
BONUS Question: Why no “F”?
luvflyin
Touchdown! Greaser!
luvflyin
Touchdown! Greaser!
Alphabet soup airspace didn’t come about until much later than that Chart. Early 90’s I think.But, On that chart there are no class A, B, C, D, E, or G airspace. But I do see uncontrolled airspace, controlled airspace, and ATA/CZ. (what it was in the '70s)
RussR
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Larry in TN
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What’s the difference between u controlled F and uncontrolled G?
Larry in TN
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I don't know a simple answer. Check the information in this article. https://en.wikipedia.org/wiki/Airspace_class