November 1, 2013

Ms. Peggy Gilligan

Associate Administrator for Aviation Safety 

Federal Aviation Administration

800 Independence Avenue, SW

Washington, DC 20590

Subject: Petition for Rulemaking – 14 CFR 121.333(c)(3)

Dear Ms. Gilligan:

Airlines for America (A4A), the Air Line Pilots Association, International (ALPA), the Regional Airline 

Association (RAA), and the National Air Carrier Association (NACA) submit this joint petition for 

rulemaking to change 14 CFR § 121.333(c)(3) which states: 

Notwithstanding paragraph (c)(2) of this section, if for any reason at any time it is necessary for 

one pilot to leave his station at the controls of the airplane when operating at flight altitudes above 

flight level 250, the remaining pilot at the controls shall put on and use his oxygen mask until the 

other pilot has returned to his duty station. 

We respectfully request to change “flight altitudes above flight level 250” in this regulation to read “flight 

altitudes above flight level 410.” There are a number of reasons that we believe that this rulemaking is 

reasonable and needed: 

 Safety is assured at a higher maximum altitude because of technological advances

 The current rule is not in harmony with International Civil Aviation Organization (ICAO)

International Standards and Recommended Practices (SARPS)

 The rule restricts visibility and movement of Federal Flight Deck Officers (FFDOs) and all pilots at 

their duty stations

 The rule creates the potential for premature failure of mask materials

 The current procedures place pilots at increased risk of contracting transmissible diseases

Safety is Assured at a Higher Maximum Altitude

The current regulation dates from the age of older air carrier transport aircraft, prior to the use of quickdon oxygen masks and the advances in today’s aircraft design and construction methods and materials. 

Depressurization of commercial aircraft at altitudes above FL 250 is an extremely rare event and history 

demonstrates that unless a catastrophic failure occurs, it does not result in injuries or significant safety 

risks for passengers or crew. 

Historical studies indicate that the time of useful consciousness (TUC) ranges from three to five minutes 

at FL 250 and 15-20 seconds at FL 410. For example, Mark Wolff’s 2006 article, Cabin Decompression 

and Hypoxia cites the well-known TUC table below.

1

 In fact, Airbus,2the Australian Transport Safety 

 

1

Found at http://www.theairlinepilots.com/medical/decompressionandhypoxia.htm

2

Found at http://www.airbus.com/fileadmin/media_gallery/files/safety_library_items/AirbusSafetyLib_-FLT_OPS-CAB_OPSSEQ09.pdf, page 5.
2

Bureau,3and the FAA in its Pilot Handbook for Aeronautical Knowledge,4and recently issued Advisory 

Circular (AC) 61-107B,5all recognize this table.

Time of Useful Consciousness

Altitude (feet) Consciousness 

15,000 

18,000 

22,000 

25,000 

28,000 

30,000 

35,000 

40,000 

45,000 

50,000 

30 minutes or more 

20-30 minutes 

5-10 minutes 

3-5 minutes 

2.5-3 minutes 

1-3 minutes 

30-60 seconds 

15-20 seconds 

9-15 seconds 

6-9 seconds 

Pressure and Altitude

Altitude (feet) Pressure 

 hpa lb/in2 Temperature oC 

0 

5,000 

10,000 

15,000 

20,000 

25,000 

30,000 

35,000 

40,000 

1013.25 

843.1 

696.8 

571.8 

465.6 

376.0 

300.9 

238.4 

147.5 

14.70 

12.23 

10.11 

8.29 

6.75 

5.45 

4.36 

3.46 

2.72 

+15.0 

+5.1 

-4.8 

-14.7 

-24.6 

-34.5 

-44.4 

-54.2 

-56.5 

If granted, this petition would require that pilots don a mask between 15-20 seconds, when the extremely 

rare sudden decompression event takes place or even longer if a subtle decompression takes place. 

Response to a rapid decompression event is routinely practiced in simulator training and with today’s 

quick-don masks, pilots are able to place the mask on properly and start the flow of oxygen well under the 

TUC for this range of altitudes. An FAA study from 1996 concludes it takes pilots an average of 5 

seconds and no more than 6.29 seconds to don masks, giving pilots more than enough time to don a 

mask at the 40,000 flight level.6

In addition to having more than enough time to don a mask, rapid decompression events are extremely 

rare. Since 1996, US air carriers have experienced six (6) incidents of rapid decompression. There have 

been approximately 168 million operations during that period which results in an incident rate of one 

event per 28 million operations. Thus, the probability of a decompression during any given flight is less 

than 10-8. However, the probability of a non-catastrophic decompression during a given flight (1) which 

results in a cabin atmosphere capable of rapidly incapacitating a pilot (2) while only one pilot is at the 

controls and (3) the single pilot at the controls is incapable of putting on a quick-don oxygen mask within 

5 seconds (as required by FAR 91.211(b)) is significantly less than “extremely improbable” (i.e., less than 

 

3

Found at http://www.skybrary.aero/bookshelf/books/957.pdf, page 5.

4

Available at http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/media/PHAK%20-

%20Chapter%2016.pdf, Chapter 16, page 3.

5

Available at http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_61-107B.pdf, page 24.

6

Available at http://www.faa.gov/data_research/research/med_humanfacs/oamtechreports/1960s/media/AM66-20.pdf,

page 1.
3

10-9). It should be noted that the effects of catastrophic decompressions are clearly outside the scope of 

what FAR 121.333(c)(3) is intended to address.

 

More recently, a review of National Transportation Safety Board (NTSB) safety information published 

since 2004 reveals only three (3) rapid decompression events in air carrier operations. These occurred 

either during climb out or when entering cruise flight. The flight crewmembers were able to quickly 

descend and there were no injuries in these events. These rapid decompression events occurred early in

the flight profile with crewmembers at their stations. This further demonstrates the extreme improbability 

of such an event occurring when one crewmember is absent from their duty station. 

Harmonization with ICAO International SARPS 

According to ICAO International Standards and Recommended Practices (SARPS), Annex 6, Operation 

of Aircraft, Chapter 4.4.5.2, Use of Oxygen, there is no requirement to routinely don the oxygen mask 

when above 25,000 feet MSL. The standard states,

All flight crew members of pressurized aeroplanes operating above an altitude where the 

atmospheric pressure is less than 376 hPa [25,000 feet] shall have available (emphasis added) at 

the flight duty station a quick-donning type of oxygen mask which will readily supply oxygen upon

demand.

In conformance with the ICAO rules, Section 605.32(3) of the Canadian Aviation Regulations states, 

The pilot at the flight controls of an aircraft shall use an oxygen mask if (a) the aircraft is not 

equipped with quick-donning oxygen masks and is operated at or above flight level 250; or (b) the 

aircraft is equipped with quick-donning oxygen masks and is operated above flight level 410.7 

It is noteworthy that the FAA permits foreign air carriers to operate in U.S. airspace using the ICAO 

standard cited above; foreign pilots are not required to wear quick-donning oxygen masks above flight 

level 250 in U.S. airspace when only one pilot is at the controls.

FFDO and General Security Implications

Current regulations require that masks be donned above flight level 250 by the pilot remaining at a duty 

station whenever the other pilot leaves the flight deck. When a quick-donning oxygen mask is in place, 

the pilot’s visibility and movement is greatly restricted. When a pilot leaves the flight deck, there are 

procedures in place to protect access to it from individuals with hostile intent. If the pilot remaining at the 

flight controls is a Federal Flight Deck Officer (FFDO), he or she provides an additional measure of flight 

deck security. With the mask in place, however, it may be difficult for an FFDO or any other pilot to quickly 

and properly respond to a threat to the flight deck. The use of an oxygen mask in these situations may 

contribute to a degradation of aviation security responsiveness during an actual crisis situation.

Failure of Mask Materials

Despite considerable expense, quick-don oxygen masks are not designed for routine, everyday use. The 

clear mask material and attachments are subject to excessive wear and tear that degrades the 

effectiveness of the mask when used during a rapid decompression. Airline experience has been that with 

extensive, routine handling, oxygen masks tend to have problems with, and failure of the valves. Also, the 

integrated visors become scratched and visibility is impaired with repeated placement into and out of their 

containers. 

The current regulation creates the unintended consequence of prematurely wearing out this necessary 

safety equipment by requiring unnecessary and frequent use at lower flight levels and thereby increases 

the risk that it may not be useable when it is needed in an actual emergency.

 

7

Found at: http://www.tc.gc.ca/eng/civilaviation/regserv/cars/part6-605-2438.htm
4

Transmissible Disease

The risk of transmissible disease arises due to the design of the pilot oxygen masks, which precludes 

them from being properly disassembled and cleaned between uses. The National Institute of 

Occupational Safety and Health (NIOSH) and the Center for Disease Control (CDC) have stringent 

guidance and regulations for the operation and cleaning of respirators between multiple users. While 

aircraft oxygen masks are not defined as respirators, logic dictates that the health risks associated with 

the sharing of respirators would apply equally to the sharing of oxygen masks. 

Several types of diseases may be communicable through sharing of oxygen masks:

 Influenza – According to the CDC, influenza is thought to be spread through coughing or 

sneezing of people infected with the influenza virus. People may also become infected by 

touching something with influenza viruses on it and then touching their mouth, nose, or eyes. 

Respiratory droplets, as well as airborne transmission are likely paths for transmission of the 

H1N1 virus. The H1N1 virus has been determined to have a life span of 2-8 hours on a hard 

surface.8 With current oxygen mask procedures, the risk of passing this virus between pilots is 

quite high. 

 Methicillin-resistant Staphylococcus aureus bacteria (MRSA) – MRSA is a deadly bacterium that 

has spread outside hospitals into the community; it now kills more people annually than AIDS. It 

is a rapidly spreading infection that can require amputation and even cause death. MRSA 

bacteria can live for weeks or months on a hard surface.9

 Meningitis – Meningitis is spread by exchange of respiratory and throat secretions. Bacterial 

infection is more severe and can cause brain damage, hearing loss, limb amputation, or death. 

CDC recommends that people not share eating utensils or water bottles to avoid transmitting the 

bacteria.10 This recommendation can be extrapolated to include oxygen masks since respiratory 

secretions will remain on them after use.

 Various bacteria – Other, various bacteria found in the environment are becoming increasingly 

resistant to antibiotics, such as c. difficile11 or pseudomonas aeruginosa,

12 which are opportunistic 

when a person’s immune system is compromised. 

 Mold – According to oxygen mask manufacturers, mold growth can be a serious health risk 

because bacteria can quickly reproduce on the surface of a moisture-laden mask or cannula. 

Mold can be forced deep into the lungs during use and cause serious health problems.13

Disinfectant wipes are used in the airline industry, when available, to clean masks. They are somewhat 

effective against most viruses when they are reachable. However, as it relates to the oxygen mask, its 

effectiveness is limited due to the need to subject the mask to the wet solution for an adequate period of 

time. The microphone, where respiratory fluids accumulate, and the inside of the oxygen supply hose are 

completely inaccessible to the disinfectant. Compounding the problem is the fact that the active ingredient 

in many disinfectant wipes, benzalkonium chloride (BC), has been shown to be a factor in creating “super 

bacteria” that are becoming more resistant to antibiotics.14 Allergic reactions have also been reported with 

continuous long-term use in sensitive users, especially on mucous membranes and unfortunately, the 

wipes are less effective against certain types of bacteria.15 Finally, there is also concern that the wipes 

have the potential to spread the pathogen to a wider area when wiping.

 

8

See http://www.cdc.gov/flu/about/qa/preventing.htm

9

See http://www.cdc.gov/mrsa/

10 See http://www.cdc.gov/meningitis/index.html

11 See http://www.cdc.gov/hai/organisms/cdiff/cdiff_infect.html

12 See http://www.cdc.gov/hai/organisms/pseudomonas.html

13 One member reports mold in about 3% of oxygen masks.

14 See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC129876/

15 See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3517330/
5

Summary

FAR 121.333(c)(3) should be amended to reflect the significant advances in aircraft and oxygen mask 

design and construction that have come into use since the regulation was first promulgated. Doing so 

would harmonize U.S. regulations with pertinent ICAO SARPS and with the oxygen mask-related 

practices of non-U.S. airlines operating in U.S. airspace.

A change would also reflect the negligible risk associated with oxygen mask use, with or without two or 

more pilots on the flight deck, and it would result in a safer and more healthful working environment for 

airline pilots. It would provide an additional measure of flight deck security and protect the integrity and 

maintainability of quick-don masks so that they will be available when needed. 

Petition

For the above-cited reasons, we petition for a change to FAR 121.333(c)(3), “Use of oxygen masks by 

flight crewmembers.” Currently, the rule requires that when a pilot leaves his station at the controls of the 

airplane for any reason, when operating at flight altitudes above flight level 250, the remaining pilot at the 

controls shall put on and use his oxygen mask until the other pilot has returned to his duty station. We 

request that the regulation be amended to change the flight altitude requirement cited in this regulation 

from “above flight level 250” to “above flight level 410.”

We further request that the FAA grant an exemption from the current rule to all FAR Part 121 aircraft 

operators upon their request. This exemption is needed to enhance safety and security until such time as 

changes to FAR 121.333(c)(3) are finalized.

Thank you for your consideration.

Sincerely,

Nicholas E. Calio Captain Lee Moak

President and CEO President

Airlines for America Air Line Pilots Association, International

 

Roger Cohen A. Oakley Brooks

President President

Regional Airline Association National Air Carrier Association