Henning said:
Hmmm, since Pt 137 is included, that would seem to take navigable airspace right down to the deck.
You'd think, but it is not so. The U.S. Supreme Court and the U.S. Court of Federal Claims seem to have disregarded Part 137 when determining the boundaries of "Navigable Airspace".
Here's what I found about "navigable airspace" as it was determined by the courts over the years (bear with me):
It all starts with what appears to be the first case taken to the Supreme Court (all other cases seem to refer to it as the historical foundation) - United States v. Causby[1] in 1946 when the applicable statute defined navigable airspace as "airspace above the minimum safe altitudes of flight prescribed by the Civil Aeronautics Authority." At that time the regs read differently too, so the court stated:
The minimum prescribed by the Authority is 500 feet during the day and 1,000 feet at night for air carriers (Civil Air Regulations, Pt. 61, §§ 61.7400, 61. 7401, Code Fed. Reg. Cum. Supp., Tit. 14, ch. 1), and from 300 feet to 1,000 feet for other aircraft, depending on the type of plane and the character of the terrain. Id., Pt. 60, §§ 60.350-60.3505, Fed. Reg. Cum. Supp., supra.
Hence, the flights in question were not within the navigable airspace which Congress placed within the public domain.So at that time, the courts considered those the lower limits on navigable airspace. Of course congress changed the statutes and the CAR were changed too, and as best I can tell Part 137 flight rules had reached their current form (roughly) in the mid 1960s. That changed things ... not much at all!
The next interesting case I find, in 1962, possibly before Ag flight rules were near their current form, is Griggs v. Allegheny County[2] . Supreme court case again:
Following the decision in the Causby case, Congress redefined "navigable airspace" to mean "airspace above the minimum altitudes of flight prescribed by regulations issued under this chapter, and shall include airspace needed to insure safety in take-off and landing of aircraft." 72 Stat. 739, 49 U. S. C. § 1301 (24). By the present regulations the "minimum safe altitudes" within the meaning of the statute are defined, so far as relevant here, as heights of 500 feet or 1,000 feet, "[e]xcept where necessary for take-off or landing."No mention of ag operations. Statute wording is close to that in use today. Navigable airspace lower bounds seem set to those of Part 91 and no where else.
Moving forward to a contemporary case, from 2012, Andrews v. United States[3] it appears the courts have settled on a definition of "navigable airspace" that disregards regs of narrow applicability like Part 137. Quoting at length from Andrews notes:
Despite this precedent for finding that a taking could occur within navigable airspace, courts have continued to apply a rule that certain flights within navigable airspace (because they are above the minimum altitudes of flight prescribed by the regulations)—that is, flights above 500 feet for noncongested areas and 1000 feet for congested areas—do not constitute a taking. See Argent, 124 F.3d at 1281 (citing, inter alia, Lacey v. United States, 219 Ct. Cl. 551, 554, 595 F.2d 614, 616 (1979) (per curiam) (applying 500-foot rule)); see, e.g., Persyn v. United States, 34 Fed. Cl. 187, 195 (1995) ("Airspace above 1,000 feet in the congested areas of cities, towns or villages, and 500 feet in uncongested areas, is navigable, or public, airspace, and the owner of subadjacent land has no claim for compensation for its use." (internal citations omitted)), aff'd on other grounds, 106 F.3d 424 (Fed. Cir. 1996).
So the courts seem to have repeatedly used the altitudes of 91.119 as the lower boundaries of navigable airspace and that appears to be the current definition.
And in all those cases, the courts have found that owners of the land do have an unfettered access to the superadjacent non-navigable airspace and that they should be compensated when anyone impedes their access and use of that airspace. This would include regulations prohibiting, for example, flying of model airplanes and similar uses. Such regulations would be equivalent to taking private property without compensation. Not allowed by the constitution.
[1]
http://scholar.google.com/scholar_case?q=navigable+airspace&hl=en&as_sdt=6,38&case=17209011020287234065&scilh=0
[2]
http://scholar.google.com/scholar_case?q=navigable+airspace+causby&hl=en&as_sdt=6,38&case=18119954310347127834&scilh=0
[3]
http://scholar.google.com/scholar_case?q=navigable+airspace+causby&hl=en&as_sdt=6,38&case=13228308468203047963&scilh=0
