AFS-11-351-E

Exemption No. 10827

UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

WASHINGTON, DC 20591

 

In the matter of the petition of 

 

DELTA AIR LINES, INC. Regulatory Docket No. 2011-0618

 

for an exemption from § 121.333(e)(2) 

of Title 14, Code of Federal 

Regulations 

DENIAL OF EXEMPTION

 By letter dated June 6, 2011, Mr. Stephen M. Dickson, Senior Vice President Flight 

Operations, Delta Air Lines, Inc., (Delta), P.O. Box 20706, Atlanta, GA 30320 petitioned the 

Federal Aviation Administration (FAA) on behalf of Delta for an exemption from 

§ 121.333(e)(2) of Title 14, Code of Federal Regulations (14 CFR). The proposed exemption, 

if granted, would allow Delta aircraft, following a cabin depressurization event, to initially

descend to 14,000 feet and subsequently descend to 10,000 feet no later than 30 minutes after

the initial depressurization event, without carrying the additional supplemental oxygen 

required by §121.333(e)(2). 

The petitioner requests relief from the following regulation:

Section 121.333(e)(2), prescribes, in pertinent part, that supplemental oxygen for emergency 

descent and for first aid; turbine engine powered airplanes with pressurized cabins, states in 

pertinent part:

(e) Passenger cabin occupants. When the airplane is operating at flight altitudes above 

10,000 feet, the following supply of oxygen shall be provided for the use of passenger cabin 

occupants:

(2) When an airplane is operated at flight altitudes up to and including flight level 250 and 

cannot descend safely to a flight altitude of 14,000 feet within four minutes, or when an 
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airplane is operated at flight altitudes above flight level 250, oxygen shall be available at the 

rate prescribed by this part for not less than 10 percent of the passenger cabin occupants for 

the entire flight after cabin depressurization, at cabin pressure altitudes above 10,000 feet up 

to and including 14,000 feet and, as applicable, to allow compliance with §121.329(c)(2) and 

(3), except that there shall be not less than a 10-minute supply for the passenger cabin 

occupants.

The petitioner supports its request with the following information:

The petitioner states in its petition for exemption that the last amendment to the passenger 

supplemental oxygen carrying requirements was in 1958. The amendment established a 

requirement to supply supplemental oxygen for 10 percent of the passengers for the entire 

time the aircraft cabin altitude is above 10,000 feet mean sea level (MSL) up to and including 

14,000 feet MSL after a depressurization event. This part of the rule applied to aircraft 

certified to operate to 25,000 feet MSL that could not descend to 14,000 feet MSL within 

4 minutes or any aircraft operating above 25,000 feet MSL. For the maximum size of aircraft 

operating at that time the rule would require the carriage of supplemental oxygen for 

approximately 15 passengers if the aircraft could not descend to 10,000 feet MSL after a 

depressurization event and the normal passenger oxygen system supply was not enough for 

the time above 10,000 feet MSL. This would generally require the carriage of 15 portable 

oxygen bottles.

Manufacturers design most modern aircraft to descend from the maximum certified altitude to 

14,000 feet MSL within 4 minutes with enough supplemental oxygen to reach 10,000 feet 

within the normal passenger oxygen system supply. Passenger oxygen systems are certified to 

a minimum of 12 minutes for aircraft operated by the petitioner. In many areas of its 

operations the petitioner has specifically designed depressurization routes that allow the 

aircraft to descend to 10,000 feet MSL within the 12-minute passenger oxygen supply to 

comply with §121.333(e)(2). Once at or below 10,000 feet MSL oxygen is no longer required 

for compliance with §121.333(e)(2). Depending on the airplane location and surrounding 

terrain, these routes may require the aircraft to be operated below grid MORAs (Minimum Off 

Route Altitudes) on defined routes. In layman’s terms, this procedure often requires the pilots 

to navigate around areas of high terrain instead of flying above the terrain.

The petitioner operates to over seventy countries within six continents. The petitioner states it 

consistently uses its Safety Management System (SMS) to identify hazards and reduce risks to 

its operation. Due to its global network, its flight crews could operate in many theaters 

spanning six continents in a given month. This makes the petitioner unique compared to the 

majority of other air carriers who do not need to prepare their flight crews for such a diverse 

operation. Using its internal risk assessments, SMS, and pilot training programs the petitioner 

develops procedures and curricula to prepare its crews, which are described later in the 

petition. One of these procedures and challenges is operating over critical terrain. Ninety-five 

percent of the routes operated by the petitioner allow an immediate descent to 10,000 feet 

MSL after a depressurization. However, approximately five percent of the operation is over 
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critical terrain airspace where the grid MORAs are above 10,000 feet and immediate descent 

to 10,000 feet is not possible without being established on a published airway or the 

engineered route designed by the petitioner. These areas are primarily in Western Canada, 

Central America, South America, the Middle East, the Himalayas and Greenland.

The petitioner states a depressurization event is a higher risk situation. The flight crew must 

don oxygen masks, deal with the situation that caused the depressurization, perform an 

emergency descent to a safe altitude and, if over critical terrain, transition to a critical terrain 

route in order to avoid the terrain while descending to 10,000 feet MSL within the time 

limitation of the passenger supplemental system. In certain parts of its network, such as South 

America, pilots face the likelihood of executing these critical terrain procedures at night or in 

the weather, greatly adding to the complexity of the maneuver and exacerbating the challenge 

of maintaining situational awareness.

In order to comply with §121.333(e)(2), the petitioner employs three methods:

1. Avoid the critical terrain areas where descent to 10,000 MSL is not possible within 

the supply of the onboard oxygen system. This option creates less efficient routes.

2. Operate over the terrain where immediate descent to 10,000 feel MSL is not 

possible but provide the crews with specific critical terrain diversion routes that 

allow initial descent to 14,000 feet then further descent to 10,000 feet MSL within 

the time of standard oxygen supply (normally 12 minutes).

3. Certain fleets have been configured with additional supplemental oxygen to allow 

additional time to remain at 14,000 feet MSL. All of the B-777 aircraft operated by 

Delta carry 32 bottles of supplemental oxygen. For certain B-767-300 aircraft, Delta 

has the capability to place a minimum of 24 supplemental bottles in specially 

configured overhead bins. In this case the bottles take up overhead passenger carryon storage capacity by at least six bins. The cost to carry the extra oxygen bottles in 

direct fuel cost for the B-777 is $339,212.00 annually based on fuel price as of 

March 23, 2011. This is fuel that is burned in order to carry the extra weight. In 

addition to the increased cost and fuel burn, the carriage of the additional oxygen 

bottles increases Delta’s carbon footprint and is not environmentally friendly.

Through its Safety Management System (SMS), the petitioner has previously identified 

operations over high terrain as an increased risk operation. Currently the petitioner has 

implemented several risk mitigation elements. These include:

• Theater Qualification for the pilots;

• Pilot qualification training and continuing qualification training with respect to critical 

terrain procedures;

• Engineered terrain avoidance routes;
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• Flight planning system identifying to the flight crews when a route requires special

depressurization routes; and

• Aircraft theater equipment restrictions requiring certain operational equipment above

regulatory requirements, e.g., not always allowing Minimum Equipment List (MEL) 

relief for enhanced ground proximity warning systems depending on the planned route.

While these mitigations make operations in areas of high terrain acceptable, the petitioner 

states there is still the latent condition of controlled flight into terrain (CFIT) inherent anytime 

the aircraft is required to operate below a grid MORA. Raising the initial descent to 

14,000 feet MSL for 30 minutes removes the vast majority of CFIT risk associated with 

critical terrain areas. In its request, the petitioner attached 8,000 foot MSL and 12,000 foot 

MSL maps for parts of South America, Middle East and Greenland. They illustrate the 

reduction of the terrain risk by initially descending to 14,000 feet MSL versus the current 

requirement to descend to 10,000 feet MSL.

The petitioner further states the likelihood of a rapid decompression event is extremely low 

and the likelihood of a rapid decompression occurring over critical terrain is even lower. The 

petitioner states therefore granting relief from the requirements of §121.333(e)(2) would be 

inconsequential, based on event probability alone. The petitioner states the FAA has affirmed 

the low probability of a decompression event in its rulemaking to temporarily deactivate the 

supplemental oxygen system in aircraft lavatories.

The petitioner states the request for relief is not precedent setting in that the FAA has 

previously granted deviation from the requirements of §121.333(e)(2) utilizing 14 CFR 

§119.55. The petitioner was granted Operations Specifications A525, Oxygen Supply: 

Passenger Cabin Occupants. In this deviation the FAA granted relief from §121.333(e)(2) for 

up to 20 minutes for international supplemental operations associated with Iraqi Freedom.

The petitioner states it has identified a hazardous materials risk associated with carrying large 

quantities of oxygen. The petitioner states in the event several of the oxygen bottles were 

turned on in a confined space with other flammable materials, the area could ignite creating a 

severe fire and possible explosion. 

The petitioner states they have configured certain fleets with additional supplemental oxygen 

to allow additional time to remain at 14,000 feet MSL. All of Delta’s B-777 aircraft carry 32 

supplemental oxygen bottles. In addition, Delta’s B-767-300 aircraft have the capability to 

place a minimum of 24 supplemental oxygen bottles in specially configured overhead bins. 

The petitioner states they are at an economic disadvantage to foreign operators because the 

foreign operators have less stringent oxygen requirements.

A summary of the petition was published in the Federal Register on June 29, 2011 

(76 FR 38266). Five comments were received.
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Four comments from Delta Airlines, Inc. flight operations management were received in 

support of granting the exemption. One comment was received from the Delta Air Line Pilots 

Association Central Air Safety Committee in support of the petition.

The FAA requested additional information about the demographics of Delta passengers from 

Delta, which was submitted to the Docket No. FAA-2011-0618-0008 (www.regulations.gov) 

on September 9, 2011. 

The FAA's analysis is as follows:

The FAA finds the issuance of an exemption to §121.333(e)(2) would be precedent-setting. 

After a review of the petitioner’s request and supporting information, the FAA has determined 

that the petitioner has not identified how its proposal would not adversely affect safety or how 

a grant of exemption would provide a level of safety at least equal to that provided by 

§ 121.333. 

The requirements of § 121.333 recognize a difference between non-emergency flight between 

10,000 and 14,000 feet as addressed in § 121.329, and flight at these altitudes following a 

decompression and subsequent rapid descent. In fact, at the time the FAA promulgated the 

requirements, subsequently incorporated into § 121.333, it noted that turbine-powered 

airplanes may require continued cruise at an altitude demanding sustaining oxygen to enable 

the airplane to reach a suitable landing field. 

The petitioner has requested a grant of exemption to permit its pilots to descend to 14,000 

feet, and then subsequently descend to 10,000 no later than 30 minutes after the start of the 

decompression event. The additional time above 10,000 would permit the petitioner’s aircraft 

to clear terrain and reduce the risk of controlled flight into terrain (CFIT) in certain critical 

terrain airspace. 

The petitioner has stated the installed drop-down oxygen system will provide oxygen to 

100 percent of the passengers for the first 12 minutes following the decompression event. The 

petitioner did not propose to provide supplemental oxygen to passengers for the remaining 18 

minutes between the cessation of the drop-down oxygen and the descent to 10,000 feet. 

Section 121.333 would require oxygen for 10 percent of the cabin occupants during those 18 

minutes. Ultimately, the petitioner’s proposal to keep an airplane at an altitude above 10,000 

feet to remain clear of terrain and obstacles would expose passengers to higher cabin altitude 

without sustaining oxygen. The FAA believes this proposal unacceptably transfers risk to the 

passengers. 

In considering this petition, the FAA conferred with physicians from the Office of Aerospace 

Medicine and physiologists within its Civil Aerospace Medical Institute (CAMI) to determine 

any medical implications from the petitioner’s proposal. They concluded that exposure to 

altitudes between 10,000 and 14,000 feet for 30 minutes, without supplemental oxygen, can 
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be tolerated by a healthy individual. However, such exposure may present a serious problem 

for passengers with compromised cardiovascular and pulmonary function following a 

decompression event. Depending on the severity of the passenger’s condition, these 

individuals may tolerate exposure at 10,000 feet, but may have serious problems at 14,000 

feet. Additionally an increasingly older flying population will predictably have more medical 

conditions that are affected by hypoxia at 14,000 feet. Following a decompression and rapid 

descent, the standard care for typical passenger injuries includes the provisions of continuous 

supplemental oxygen, making the carriage of supplemental oxygen necessary. Based on the 

information provided by the petitioner, CAMI determined a grant of exemption would result 

in a marginally increased aeromedical risk. 

The petitioner states the FAA has previously granted a similar exemption when it issued 

operations specification (OpSpec) A525. The FAA issued OpSpec A525 to support essential 

operations for the national defense on behalf of the Department of Defense, in accordance 

with §119.55. Those operations carried military personnel physically fit for combat. As 

identified by the petitioner, its passenger demographics do not match those assumed in the 

issuance of OpSpec A525. Additionally, it contained limitations that prohibited its use in 

aeromedical evacuation operations, operations involving the carriage of non-military 

passengers and any other passenger-carrying operation conducted by the certificate holder. 

Furthermore, it allowed operation between 14,000 and 10,000 feet for a maximum of 

20 minutes, not 30 minutes as proposed in this petition. Neither the passenger demographics, 

nor the operational mission, are the same as the operations permitted by OpSpec A525. 

The petitioner has stated that the likelihood of a rapid decompression event is extremely low 

and the likelihood of a rapid decompression occurring over critical terrain is even lower. The 

FAA reviewed data to determine the number of decompression events resulting in rapid 

(emergency) descents. Data collected from the Service Difficulty Report System showed 66 

decompression events to include explosive, rapid, slow or gradual decompression events in 

part 121 operations over the previous five years or approximately one occurrence per month. 

The FAA does not believe the likelihood of one occurrence per month represents low risk. 

Additionally, while the FAA did determine it was appropriate to deactivate the supplemental 

oxygen system in response to a security vulnerability, the FAA permitted this in the lavatory 

only and for a limited duration. The FAA is currently working on rulemaking to restore 

supplemental oxygen to the lavatories.

The petitioner has already developed procedures to mitigate the risk of flying over critical 

terrain to include additional training, flight planning, and restrictions on deferral of 

equipment. The petitioner has not proposed any mitigation to address the absence of 

supplemental oxygen and the FAA has determined the additional risk to passengers presented 

by the lack of supplemental oxygen is not in the public interest. 

The petitioner’s determination that a hazardous materials risk is associated with the carriage 

of large amounts of oxygen is unfounded. All aircraft in the petitioner’s fleet already carry 

additional oxygen supplies. The FAA has already addressed the risks associated with the 
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carriage of oxygen. Oxygen bottles are manufactured in accordance with FAA-approved 

standards detailed in Technical Standard Orders and are installed and maintained in 

accordance with FAA-approved procedures.

The FAA has considered petitioner’s statement that foreign operators have less stringent 

supplemental oxygen rules and notes that the statement is correct as it relates to operators 

operating under EASA regulations, but not as it relates to all foreign operators. However, a 

difference in regulatory standards between States does not justify an exemption to a single 

U.S. operator. The regulation cited by petitioner (14 CFR § 121.333(e)(2))1 requires 

supplemental oxygen for at least 10 percent of the passengers for the entire flight at altitudes 

between 10,000 feet and 14,000 feet following descent to those altitudes because of a 

depressurization event. Flight at or below 10,000 feet does not require supplemental oxygen. 

The International Civil Aviation Organization (ICAO) Standards and Recommended Practices 

found in Section 4.3.8.1(b) of Annex 6, is not limited to post-depressurization events and, 

states that 10 percent of the passengers should have supplemental oxygen after 30 minutes of 

flight between 10,000 feet and 13,000 feet.2

 Under this standard, level-off at 14,000 feet 

requires supplemental oxygen for all passengers for any period at that altitude. This is more 

restrictive than the cited U.S. regulation.

For those operators operating under the European Aviation Safety Agency (EASA) 

regulations, the applicable EASA rule, CAT.IDE.A.235 Supplemental oxygen — pressurized 

airplanes, requires supplemental oxygen for at least 10 percent of the passengers for the 

“remainder of the flying time when the cabin pressure altitude exceeds 10,000 feet but does 

not exceed 14,000 feet, after the initial 30 minutes at these altitudes.”3 This is less restrictive 

 1 Sec. 121.333 Supplemental oxygen for emergency descent and for first aid; turbine engine powered 

airplanes with pressurized cabins.

(e) Passenger cabin occupants. When the airplane is operating at flight altitudes above 10,000 feet, the 

following supply of oxygen must be provided for the use of passenger cabin occupants:

(2) When an airplane is operated at flight altitudes up to and including flight level 250 and cannot descend 

safely to a flight altitude of 14,000 feet within four minutes, or when an airplane is operated at flight altitudes 

above flight level 250, oxygen must be available at the rate prescribed by this part for not less than 10 percent 

of the passenger cabin occupants for the entire flight after cabin depressurization, at cabin pressure altitudes 

above 10,000 feet up to and including 14,000 feet and, as applicable, to allow compliance with §121.329(c) 

(2) and (3), except that there must be not less than a 10-minute supply for the passenger cabin occupants.

2 ICAO Standards and Recommended Practices (SARP)Annex 6, 4.3.8.1(b)

Gen. Reg. 7.9.1.13(a) Table 1

Annex Reference & SARP Identifier: 06-0000027600

Oxygen Supply

A flight to be operated at flight altitudes at which the atmospheric pressure in personnel compartments will be 

less than 700 hPa shall not be commenced unless sufficient stored breathing oxygen is carried to supply:

a) all crew members and 10 percent of the passengers for any period in excess of 30 minutes that the 

pressure in compartments occupied by them will be between 700 hPa and 620 hPa; and

b) the crew and passengers for any period that the atmospheric pressure in compartments occupied by them 

will be less than 620 hPa.

3 CAT.IDE.A.235 Supplemental oxygen — pressurized airplanes

(a) Pressurized airplanes operated at pressure altitudes above 10,000 ft. shall be equipped with supplemental 

oxygen equipment that is capable of storing and dispensing the oxygen supplies in accordance with Table 1.

Table 1 Oxygen minimum requirements for pressurized airplanes (data extracted by author)

Supply for: 10 % of passengers
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than the cited U.S. regulation because it does allow 30 minutes of flight before supplemental 

oxygen must be provided to 10 percent of the passengers, whereas the U.S. regulation requires 

immediate availability of oxygen for 10 percent of the passengers.

The FAA’s Decision:

In consideration of the foregoing, I find that a grant of exemption would not be in the public 

interest. Therefore, pursuant to the authority contained in 49 U.S.C. §§ 40113 and 44701, 

delegated to me by the Administrator, the petition of Delta Air Lines, Inc. for an exemption 

from 14 CFR §121.333(e)(2) is hereby denied. 

Issued in Washington, D.C., on July 24, 2013

/s/

John S. Duncan

Deputy Director, Flight Standards

 Service

 

Duration and cabin pressure altitude: The remainder of the flying time when the cabin pressure altitude 

exceeds 10,000 ft. but does not exceed 14,000 ft., after the initial 30 minutes at these altitudes.
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Project No.: AFS-11-351-E

Project Officer: _______________

ARM-101:KJones:6/18/2012:Doc#34381

ARM-1/100/101:Program Office AFS-200

MR STEPHEN M DICKSON

SENIOR VICE PRESIDENT FLIGHT OPERATIONS

DELTA AIR LINES INC

PO BOX 20706

ATLANTA GA 30320