UNPUBLISHED

UNITED STATES COURT OF APPEALS

FOR THE FOURTH CIRCUIT

No. 08-2155

GEORGE WELCH FOLK; TIMOTHY BRIAN FOLK,

Petitioners,

v.

ROBERT A. STURGELL, Acting Administrator Federal Aviation 

Administration,

Respondent.

On Petition for Review of an Order of the National 

Transportation Safety Board. (SE-18005; SE-18018)

Argued: March 23, 2010 Decided: April 22, 2010

Before DUNCAN and DAVIS, Circuit Judges, and Joseph R. GOODWIN, 

Chief United States District Judge for the Southern District of 

West Virginia, sitting by designation.

Affirmed by unpublished opinion. Judge Duncan wrote the 

opinion, in which Judge Davis and Judge Goodwin joined.

Robert Giacinto Blackford, ALLEN & BLACKFORD, PC, Gaithersburg, 

Maryland, for Petitioners. Laura Jennings, FEDERAL AVIATION 

ADMINISTRATION, Washington, D.C., for Respondent.

Unpublished opinions are not binding precedent in this circuit.
2

DUNCAN, Circuit Judge:

This appeal arises from a National Transportation and 

Safety Board (“Board”) decision affirming an Administrative Law 

Judge’s (“ALJ”) determination that Petitioners George and 

Timothy Folk violated Federal Aviation Administration (“FAA”) 

regulations. The issues before this court are whether 

substantial evidence supports the finding that Petitioners flew 

over a “congested area” according to 14 C.F.R. § 137.51 and 

whether the term “congested area” violates the vagueness 

doctrine under the Due Process Clause. For the reasons that 

follow, we affirm.

I.

George Folk owns a farm in Martinsburg, West Virginia, and 

operates a crop-dusting business with his son Timothy Folk. On 

May 30, 2006, FAA Inspector George Cooper Towers received a 

complaint about Petitioners flying too low. During a routine 

inspection on June 16, 2006, Towers told Petitioners that he had 

received a complaint about low flying and warned them that they 

must submit a “congested area plan” before flying over any 

congested area. When Petitioners asked what the term “congested 

area” meant, Towers responded that no precise definition 

existed. He explained, however, that “a group of . . . as few 

as two or three houses . . . may be considered congested.” J.A. 
3

95. The significance of designating an area as congested is 

that if complaints are made with respect to an area that is 

determined to be congested, and no congested area plan has been 

filed, the FAA will initiate an enforcement action. However, 

the filing of a congested area plan is not considered an 

admission that the proposed area is indeed congested. 

On July 31, 2006, and September 9, 2006, Petitioners flew 

their plane near the intersection of Swan Pond Road and Hollida 

Lane in Martinsburg. Because they considered this area 

uncongested, Petitioners did not file a congested area plan 

before either flight. When neighbors complained about 

Petitioners’ low flying, Towers initiated enforcement 

proceedings against them. After conducting an evidentiary

hearing, the ALJ determined that Petitioners had violated FAA 

regulations because the area near the intersection of Swan Pond 

Road and Hollida Lane was, in fact, congested. The Board 

affirmed. This appeal followed.

II.

Petitioners argue that the term “congested area” violates 

the vagueness doctrine under the Due Process Clause, and that 

substantial evidence does not support the determination that 

they flew over a congested area. In order to provide context 

for these issues, we begin with a discussion of the relevant 
4

regulatory framework. We then address each of Petitioners’ 

contentions in turn.

A.

FAA regulations generally prohibit low flying over 

congested areas. For example, Section 91.119 of Chapter 14 of 

the Code of Federal Regulations, which establishes “[m]inimum 

safe altitudes,” provides:

Except when necessary for takeoff or landing, no 

person may operate an aircraft below the following 

altitudes:

* * *

(b) Over congested areas. Over any congested area of 

a city, town, or settlement, or over any open air 

assembly of persons, an altitude of 1,000 feet above 

the highest obstacle within a horizontal radius of 

2,000 feet of the aircraft.

(c) Over other than congested areas. An altitude of 

500 feet above the surface, except over open water or 

sparsely populated areas. In those cases, the 

aircraft may not be operated closer than 500 feet to 

any person, vessel, vehicle, or structure.

14 C.F.R. § 91.119. This section governs “the operation of 

aircraft within the United States and within 12 nautical miles 

from the coast of the United States.” Id. § 91.101.

FAA regulations provide for more lenient treatment of

agricultural aircraft. Sections 137.49 and 137.51 of Chapter 14 

also concern minimum altitudes, but “apply to persons and 

aircraft used in agricultural aircraft operations.” Id. §
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137.29(a). Section 137.49 regulates “[o]perations over other 

than congested areas,” providing:

Notwithstanding Part 91 of this chapter, during the 

actual dispensing operation, including approaches, 

departures, and turnarounds reasonably necessary for 

the operation, an aircraft may be operated over other 

than congested areas below 500 feet above the surface 

and closer than 500 feet to persons, vessels, 

vehicles, and structures, if the operations are 

conducted without creating a hazard to persons or 

property on the surface.

Id. § 137.49. Section 137.51 regulates “[o]peration over 

congested areas,” providing:

(a) Notwithstanding Part 91 of this chapter, an 

aircraft may be operated over a congested area at 

altitudes required for the proper accomplishment of 

the agricultural aircraft operation if the operation 

is conducted --

(1) With the maximum safety to persons and 

property on the surface, consistent with the 

operation; and

(2) In accordance with the requirements of 

paragraph (b) of this section.

(b) No person may operate an aircraft over a congested 

area except in accordance with the requirements of 

this paragraph.

(1) Prior written approval must be obtained from 

the appropriate official or governing body of the 

political subdivision over which the operations 

are conducted.

(2) Notice of the intended operation must be 

given to the public by some effective means, such 

as daily newspapers, radio, television, or doorto-door notice.

(3) A plan for each complete operation must be 

submitted to, and approved by appropriate 
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personnel of the FAA Flight Standards District 

Office having jurisdiction over the area where 

the operation is to be conducted. The plan must 

include consideration of obstructions to flight; 

the emergency landing capabilities of the 

aircraft to be used; and any necessary 

coordination with air traffic control.

Id. § 137.51. Subsection (b) further provides: “No person may 

operate any multiengine aircraft over a congested area below the 

altitudes prescribed in Part 91 of this chapter except during 

the actual dispensing operation, including the approaches, 

departures, and turnarounds necessary for that operation.” Id.

§ 137.51(b)(5)(iii).1

The regulations never define “congested area” or “other 

than congested area.” At the relevant time, the FAA Inspectors’ 

Handbook 8700.1 provided the only guidance:

H. Considerations for Congested Area Determinations. 

The term congested area has been applied on a case by 

case basis since it was first used. No precise 

mathematical or geographic definition has been 

developed. The rule is clear that the congested area 

must be an area of a city, town, or settlement. 

However, some guidelines have been developed to assist 

in interpretation:

(1) The purpose of the rule is to provide minimum 

safe altitudes for flight and to provide adequate 

protection to persons on the ground. The 

following areas were determined to be congested 

by the Civil Aeronautics Board, in past cases:

 1 Section 137.51(b)(5)(iii) rebuts Petitioners’ argument 

that section 91.119 was never intended to apply to agricultural 

aircraft.
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(a) Approximately 10 houses and a school,

(b) the campus of a university,

(c) a crowded beach area along a highway,

and

(d) a boy’s camp where numerous people were 

on the docks and the shore.

(2) The presence of people is important to the 

determination of whether an area is “congested.”

(3) The term is administered to prohibit over 

flights that cut the corners of large, heavily 

congested, residential areas.

(4) No definition has been constructed, which 

determines the allowable number of people, the 

amount of ground traffic, the proximity of 

buildings to each other, the number of buildings 

or residences, or other conditions that exist in 

a particular area, to both protect persons or 

property on the ground and allow agricultural 

aircraft operations to take place.

J.A. 216. The Handbook added, regarding section 137.49, that 

where “the pilot of an agricultural aircraft dispenses an 

economic poison on a field adjacent to a farmhouse,” he “may 

operate less than 500 feet above the surface or closer than 500 

feet to the house provided the house or its occupants are not 

exposed to hazard from the aircraft or the chemicals.” J.A. 

216.
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Petitioners contend that section 137.49 applies here 

because they flew over a non-congested area.2

 By contrast, the 

FAA contends that section 137.51 applies because they flew over 

a congested area. Thus the question before the ALJ was whether 

the relevant area was congested for purposes of section 137.51. 

B.

Petitioners argue that because the term “congested area” 

does not have a clear meaning, section 137.51 violates the 

vagueness doctrine under the Due Process Clause. We review this 

issue de novo.3

 2 We note, but need not decide, that section 137.49 may not 

have assisted Petitioners even if the relevant area had not been 

congested. One witness testified before the ALJ that one of the 

relevant flights caused a “loud rumble” in his house that 

sounded like “someone had hit [the] house.” S.J.A. 12. When 

the resident of the house went outside to investigate, the plane 

flew over him four different times at an altitude of about 100 

to 300 feet. The witness testified that he did not “feel safe 

having a plane flying at such altitude over [his] residence.” 

S.J.A. 16-17. These circumstances might have been interpreted 

as “creating a hazard to persons or property on the surface” 

under section 137.49. 14 C.F.R. § 137.49.

 See United States v. Williams, 364 F.3d 556, 559 

(4th Cir. 2004). 

3 Notably, the Board would have lacked jurisdiction to 

entertain Petitioners’ constitutional challenge to “congested 

area” in section 137.51. See Adm’r v. Eby, 3 N.T.S.B. 614, 615 

(N.T.S.B. 1977) (“With respect to respondent’s attack on the 

regulations as unconstitutionally vague (due to the absence of a 

definition of ‘congested area’), the Board has consistently held 

that it lacks jurisdiction to entertain attacks on the validity 

of the [Federal Aviation Regulations].”).
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Petitioners must show that the relevant section was 

impermissibly vague as applied to them.4

A statute is impermissibly vague if it either (1) 

fails to provide people of ordinary intelligence a 

reasonable opportunity to understand what conduct it 

prohibits or (2) authorizes or even encourages 

arbitrary and discriminatory enforcement. . . . 

Stated differently, a court considering a vagueness 

challenge must determine if the statutory prohibitions 

are set out in terms that the ordinary person 

exercising ordinary common sense can sufficiently 

understand and comply with.

 We have explained the 

relevant test as follows:

United States v. Whorley, 550 F.3d 326, 333 (4th Cir. 2008)

(internal quotations and citations omitted). The Supreme Court 

has explained that under certain circumstances this test should 

be applied less stringently:

These standards should not, of course, be mechanically 

applied. The degree of vagueness that the 

Constitution tolerates -- as well as the relative 

importance of fair notice and fair enforcement --

depends in part on the nature of the enactment. Thus, 

economic regulation is subject to a less strict 

vagueness test because its subject matter is often 

more narrow, and because businesses, which face 

economic demands to plan behavior carefully, can be 

 4 We assume, for purposes of our analysis, that Petitioners 

are bringing an as-applied challenge to section 137.51. 

Petitioners do not make clear whether they are bringing a facial 

or an as-applied challenge. However, a facial challenge appears 

inapplicable in this case. To make out a facial challenge, 

Petitioners would have to “demonstrate that the law is 

impermissibly vague in all of its applications.” Vill. of 

Hoffman Estates v. Flipside, Hoffman Estates, Inc., 455 U.S. 

489, 497 (1982). That cannot be done here because “congested 

area” plainly covers densely populated urban settings.
10

expected to consult relevant legislation in advance of 

action. Indeed, the regulated enterprise may have the 

ability to clarify the meaning of the regulation by 

its own inquiry, or by resort to an administrative 

process. The Court has also expressed greater 

tolerance of enactments with civil rather than 

criminal penalties because the consequences of 

imprecision are qualitatively less severe.

Vill. of Hoffman Estates, 455 U.S. at 498-99 (footnote call 

numbers omitted); see Greenville Women’s Clinic v. Comm’r, S.C. 

Dep’t of Health & Envtl. Control, 317 F.3d 357, 366 (4th Cir. 

2002). 

Petitioners cannot show that they lacked “a reasonable 

opportunity to understand what conduct [section 137.51] 

prohibits.” Whorley, 550 F.3d at 333 (quotations and citation 

omitted). Because Towers warned that two or three houses may be 

considered a congested area, Petitioners had reason to believe 

that the residential area near the intersection of Swan Pond 

Road and Hollida Lane might be congested. They could have 

resolved any doubt by filing a congested area plan for that 

intersection and waiting for Towers’s response. Furthermore, 

Petitioners have not tried to show that section 137.51 

“authorizes or even encourages arbitrary and discriminatory 

enforcement,” nor have they presented any evidence that the 

enforcement action against them was arbitrary. Id. (quotations 

and citation omitted). Therefore, Petitioners have failed to 

show that section 137.51 is unconstitutionally vague.
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C.

We next consider the ALJ’s and Board’s determination that 

Petitioners flew over a congested area. The decision below must 

be set aside if that determination is “unsupported by 

substantial evidence.” 5 U.S.C. § 706(2)(E); see North Carolina 

v. Fed. Aviation Admin., 957 F.2d 1125, 1128 (4th Cir. 1992). 

Substantial evidence is “‘such relevant evidence as a reasonable 

mind might accept as adequate to support a conclusion.’” 

Platone v. U.S. Dep’t of Labor, 548 F.3d 322, 326 (4th Cir. 

2008) (quoting Consol. Edison Co. of N.Y. v. NLRB, 305 U.S. 197, 

229 (1938)).

In this case, the Board made clear that the question of 

what constitutes a “congested area” involves a case-by-case 

inquiry that considers all relevant circumstances:

The term “congested area” will continue to be 

adjudicated on a case-by-case basis before this Board. 

The determination must take into consideration all 

circumstances, not only the size of an area and the 

number of homes or structures, but, for example, 

whether the buildings are occupied or people are 

otherwise present, such as on roads.

J.A. 276-77. This approach is consistent with the Board’s prior 

case law. See Eby, 3 N.T.S.B. at 615 (determining that an area 

was congested after “[c]onsidering the size of the area and the 

number of homes, and the corresponding density of residences, 

and after viewing the aerial photographs”). Therefore, we must 

determine whether substantial evidence supports the ALJ’s and 
12

Board’s finding that, given all relevant circumstances, the area 

near the intersection of Swan Pond Road and Hollida Lane was 

congested.

After carefully reviewing the record, we note that 

approximately thirty houses are located in the general vicinity 

of that intersection. The record further shows that 

Petitioners’ flights passed over corner sections of that area. 

We therefore conclude that the area over which Petitioners flew 

could reasonably be considered congested based on substantial 

evidence in the record. 

III.

For the reasons stated above, we 

AFFIRM.