So what is the difference between Class I and Class II airspace and why should you care? My answer has changed over the years because (a) navigation has changed over the years, and (b) the regulations are slowly catching up.
— James Albright
I used to care, because the original AC 91-70 defined it and various regulations said we had to plot based, in part, on being in Class II airspace. So this was important to us.
But then AC 91-70A changed the definition of Class I airspace to include being within the service volume of GNSS, so basically almost the entire globe. Armies of anti-plotters decided plotting wasn't needed at all. I started to think the entire argument was silly.
The most recent AC 91-70B couldn't be bothered to define Class I navigation at all and I am starting to not care about the distinction.
So does it matter if you are in the business of flying aircraft internationally? I will leave that to you. I still plot, however I do that electronically: Plotting.
Life under AC 91-70
Class I navigation: Any en route flight operation conducted in controlled or uncontrolled airspace that is entirely within operational service volumes of ICAO standard navaids (VOR, VOR/DME, NDB).
Source: AC 91-70, Ch. 8, ¶8e
This was important because it determined when you had to plot:
OLD VERSION - THIS HAS BEEN REOMOVED FROM CURRENT FAA ORDER
Plotting Procedures. Plotting procedures have had a significant impact on the reduction of gross navigational errors. There is a requirement to plot the route of flight on a plotting chart and to plot the computer position, approximately 10 minutes after waypoint passage. Plotting may or may not be required, depending upon the distance.
- Plotting procedures are required for all turbojet operations where the route segment between the operational service volume of ICAO standard ground-based navigational aids exceeds 725 NM.
- Plotting procedures are required for all turboprop operations where the route segment between the operational service volume of ICAO standard ground-based navigational aids exceeds 450 NM.
- The Administrator requires plotting procedures for routes of shorter duration that transit airspace where special conditions exist, such as reduced lateral and vertical separation standards, high density traffic, or proximity to potentially hostile border areas.
- Any existing approvals that differ from the plotting requirements in this paragraph and Class II navigation procedures should be reviewed and revised as necessary. Direction and guidance is available from the navigation specialists in coordination with AFS-400
Source: FAA Order 8900.1 Volume 4, Chapter 1, Paragraph 4-80.A
Life under AC 91-70A
Class I navigation is any en route flight operation conducted in controlled or uncontrolled airspace that is entirely within operational service volumes of ICAO standard NAVAIDs (GNSS, VOR, VOR/DME, and NDB).
Source: AC 91-70A, 10-1.i.
Now that GNSS was used to define Class I navigation, it seemed we would never be outside it, certainly not over most oceanic routes, and plotting would not ever be required! I wrote something to that effect and got a call from my good friends in the FAA who said I was mistaken because: reasons. Okay then.
Life under AC 91-70B
Source: AC 91-70B
Yup, there is nothing there. The current revision does not have any definitions for Class I or Class II airspace and the current FAA order dropped the inclusions of GNSS in what is a qualified navaid. In fact, it made specific mention of using GPS while in Class II airspace.
The following are extracts from the cited FAA Order.
4-52 VFR CLASS I NAVIGATION. VFR Class I navigation is any Class I navigation operation conducted under VFR in visual meteorological conditions (VMC).
4-53 TYPES OF VFR CLASS I NAVIGATION. The following are two types of VFR Class I navigation.
A. Pilotage. One of the primary means of conducting VFR Class I navigation is by pilotage. Pilotage is defined in 14 CFR part 1 as “navigation by visual reference to landmarks.”
B. Station-Referenced. In situations where pilotage is not appropriate, it is necessary to use other means of conducting VFR Class I navigation to locate the intended destination, avoid obstacles, and protect persons and property on the ground. This is accomplished by using electronic station-referenced (nonvisual) Navigational Aids (NAVAID), such as a very high frequency omni-directional range station (VOR), distance measuring equipment (DME), a Non-Directional Radio Beacon (NDB), Global Positioning System (GPS), or an Area Navigation (RNAV) system, with NAVAID and/or inertial navigation system (INS) navigation inputs.
4-55 IFR CLASS I NAVIGATION. A. Primary Objectives. IFR Class I navigation is any Class I navigation operation conducted under IFR.
4-76. B. En Route Flight Operation or Portion of a Flight Operation. Class II navigation is any en route flight operation or portion of a flight operation that is not Class I navigation. Any operation or portion of an en route operation is Class II navigation if it takes place outside the officially designated operational service volumes of International Civil Aviation Organization (ICAO) standard ground-based Navigational Aids (NAVAID), such as very high frequency omni-directional range (VOR), very high frequency omni-directional range station/distance measuring equipment (VOR/DME), and Non-Directional Beacons (NDB). Class II navigation depends on the use of a long-range navigation system (LRNS). An LRNS may be satellite-based (e.g., Global Positioning System (GPS)) or self-contained (e.g., inertial reference system (IRS)).
Source: FAA Order 8900.1, Volume 4, Chapter 1, Section 3
So it would seem that oceanic areas are again in Class II airspace and require Class II navigation. Do you have to plot there? I think so but there isn't a cut and dried answer: Plotting.
Advisory Circular 91-70, Oceanic and International Operations, September 1994, U.S. Department of Transportation
Advisory Circular 91-70A, Oceanic and International Operations, 8/12/10, U.S. Department of Transportation
Advisory Circular 91-70B, Oceanic and International Operations, 10/4/16, U.S. Department of Transportation