CHAPTER 6: DEEP
VEIN THROMBOSIS, SEATING AND STRESS
Seating and space
6.33 We consider those points
in more detail elsewhere in this Report, but turn immediately
to one of the most closely related issues - seating and space
- about which we have received many representations. As noted
in paragraph 3.50, the JAA and CAA regulatory requirements for
seating relate only to safety. They do not include any consideration
of passenger comfort, and there is no regulation to relate either
passenger numbers or seat spacing to the type of operation concerned.
6.34 Modern passenger airliners
are of two basic types:
(a) short-haul narrow-bodied aircraft which
generally carry between 50 and 200 passengers up to about 3,000
miles (or some 6 hours flying time) and have one central aisle
with seats distributed in single, double or triple bank rows on
either side; and
(b) long-haul wide-bodied aircraft which typically
carry between 250 and 450 passengers over longer distances of
up to about 8,000 miles
(or some 14 hours flying time) and have two cabin aisles with
double or triple bank seat rows on the outer sides and rows of
four, five or six seats between the aisles.
6.35 The basic trends of civil airliner development
have been and seem to be continuing to be towards larger aircraft
carrying more passengers for longer distances.
As a result, new routes may be opened up over remote territories
and oceans. Non-stop flight sectors in excess of 18 hours are
envisaged (Q 354). Such developments may not be welcomed universally
because of the implications for passenger health. The International
Airline Passenger Association (IAPA), for instance, was particularly
concerned about these trends (p 243). There must be concern over
whether any potentially adverse health implications of the aircraft
cabin environment will be exacerbated by the increasing size of
aircraft, the increased passenger numbers being carried in such
aircraft, and the increasing duration of non-stop flights. There
are also questions about the management of on-board safety and
medical emergencies when a future very large aircraft may be many
hours flying time from a suitable diversion airport. We are aware
that aircraft manufacturers, aviation regulators, and airlines
are studying these scenarios (p 130, Q 379), and we welcome this.
6.36 The descriptions in
paragraph 6.34 refer to aircraft configured throughout for the
basic economy or traveller class, but aircraft (particularly those
intended for scheduled services) generally provide for several
classes, greatly differentiated by ticket price. In our consideration
of seating, space and mobility, we have concentrated on economy
class passengers. They not only form the vast majority of airline
passengers but also have the least generous provision and are
thus most exposed to any potentially adverse health effects.
6.37 The profitability of an airline, like any other
form of passenger transport, depends on providing and selling
enough seats to enough customers at sufficient prices to ensure
an adequate return on capital investment and operating costs.
Thus there must be a successful balance between installing enough
seats in a fixed space at an acceptable comfort level and selling
them at a price to attract sufficient customers in a very highly
competitive market (QQ 279-295, p 243). Subject to the minimum
safety requirements for seating, space and mobility noted in paragraphs
3.49ff, the trade-off clearly seems to be between seat space and
6.38 It is not straightforward
to establish just what seat sizes are. The term "seat pitch"
is an airline term for the distance between identical fixed points
on the seat and the seat ahead, from which the calculation of
how many rows of seats fit into a certain distance is straightforward.
That measure makes no allowance for the thickness of the seat
back, and a more useful measure for passengers' information is
the distance from the seat behind the base of the spine to the
back of the seat in front: indeed, it is this measurement which
the UK safety regulators use
(QQ 289 & 290), and which Airworthiness Notice 64 requires
to be a minimum of 26 inches (paragraph 3.49). People would normally
refer to this measurement as "leg-room" but airlines
seem to use this phrase differently (QQ 281-285).
6.39 The term "seat width" is also ambiguous.
As far as elbow room is concerned, this is the lateral space available
between the centre-lines of the left and right armrests. For the
hips, however, the measure should be the distance between the
inner surfaces of the left and right armrests - perhaps, as Miss
Stringer suggested (Appendix 4) with some allowance for the audio-visual
controls that are often placed on the inside surface of one of
the armrests. The need for better definitions is discussed further
in paragraph 6.49 below.
6.40 There are some complicated
marketing considerations for operators, reflected in a range of
available seat room. The Consumers' Association submitted a copy
of a recent survey
(p 59) which found that seat pitch
in short-haul economy class ranged from 28 to 32 inches, and seat
width from 15.5 to 20 inches. In long-haul economy class, seat
pitch ranged from 28 to 34 inches and seat width from 16.2 to
18 inches. If the seat back is two inches thick, a seat pitch
of 28 inches is the bare minimum that the UK safety regulations
6.41 Seat design, space and
configuration are clearly important in marketing and competition
terms. Although we are concentrating in this section on economy
class passengers, the marketing interplay with business and first
class options cannot be ignored.
6.42 Until recently, it appears that little or no
marketing consideration was given to any potential relationship
between seat size (and associated mobility restrictions) and passenger
health. We were told by BATA (Q 279), JAA (p 130) and others that
there was no evidence that seat space, in itself, had any adverse
impact on the health of airline passengers. However, as concerns
have grown that restrictive seating might be detrimental to health,
particularly in relation to the risk of DVT, airline marketers
have begun to include health considerations as well as simple
comfort factors in their trade-off calculations (Q 277).
6.43 Representatives of the airlines assured us that
there was effective medical and passenger input into these deliberations
(QQ 276-278), and Dr Bagshaw said that British Airways were fitting
new economy seats giving better leg room in response to passenger
concerns (Q 286). This does not necessarily suggest that airlines
acknowledge a contribution from restrictive seating to health
risks, but it is to be hoped that it demonstrates that medical
input carries some weight in deliberations on the trade-offs between
seat size and price.
6.44 As demonstrated by a number of the submissions
summarised in Appendix 4, there is strong public demand for increased
seat space in economy class, generally accepting the prospect
of a modest increase in prices. In large measure, this reflects
comfort considerations as more people are flying longer distances.
It also reflects some concern over health, although perhaps among
only a small proportion of airline passengers.
6.45 Some seats with extra leg-room (front of cabin,
escape rows etc.) are already available on most flights but this
is of limited use to those passengers who might need or want them
unless they can be pre-booked. The Holiday Which? survey
mentioned in paragraph 6.40 found that extra leg-room was pre-bookable
on only about half the flights studied. The airlines said the
situation was still patchy, but they were continuing to respond
to this emerging market demand (QQ 293-296, p 104).
6.46 It is not unreasonable
for passengers to want to know, at the time of booking, what size
of seat is on offer for them to purchase. Airlines with varied
fleets may have difficulty in answering such questions because
of possible uncertainty until shortly before the flight about
which aircraft will actually be used. Even so, airlines should
know of the possible permutations. We urge airlines not only to
be more open about what it is that their customers are being sold
but also to develop the options for pre-booking seats with extra
6.47 BATA said the demand
for seats with extra space as a result of normal cabin layout
was only modest (Q 279), but we feel that this may reflect the
current uncertainty about what is actually on offer. BATA further
estimated that adding a couple of inches to existing seat pitch
would put fare prices up by about 10% (p 124). British Airways
estimated that 15-20% of economy class passengers might pay a
small premium for increased seat pitch (Q 296). These considerations
have led them, Virgin Atlantic and a number of other airlines
to introduce a super-economy class with more spacious seating
(QQ 279, 292 & 296, p 107).
6.48 We believe that the
introduction of "premium economy" seating is a good
answer to the demand for space above a reasonable minimum. We
recognise - and the industry needs fully to recognise - that there
is no such thing as a standard passenger with standard aspirations.
Indeed, we were struck by the fact that some of the more sensational
journalism about DVT and seating (on which we comment in paragraphs
8.35ff) appeared in the travel section of newspapers alongside
pages of advertisements for the cheapest flights in what must
be, almost by definition, minimum standard seating. Passengers
are, of course, free to purchase whatever seating they wish. The
point we make several times in this Report is that passengers'
choices should be properly informed.
6.49 To facilitate passengers'
choice of seating, we recommend CAA to use its current research
(as welcomed in paragraph 3.51) to develop an unambiguous set
of definitions for seat dimensions. The
key issues are: the minimum size of seat taking account of health
considerations; accommodation of passengers above average size;
and proper allowance for seat-space reductions from the seat in
front being reclined, material in seat-back pockets and fold-down
6.50 That research may also
point the way to new minimum standards. We understand BATA's concern
that UK airlines should not be disadvantaged in a diverse and
global market by a higher minimum standard than its international
competitors. That simply strengthens the arguments in paragraph
6.31 for the industry as a whole and the international regulators
to review seating arrangements.
6.51 Our concern is not only
about seat sizes but also for space to move around the cabin.
We received a number of representations (Appendix 4 and others)
that limited space for out-of-seat movement may also have a substantial
adverse impact on health. The airlines recognise the need for
movement in their various in-flight media (QQ 297 & 298).
BATA drew our attention to Britannia's practice on long-haul flights
of making an announcement about moving round the cabin when appropriate,
not least to get drinks from central water fountains (p 124).
However, Dr Bown (Appendix 4) and Ms Vivienne Williams (p 292)
are not alone in feeling that, far from encouraging passenger
exercise and mobility, the reality is that some airlines actively
discourage this. As noted in paragraph 6.31(f), we look to the
regulators and the industry as a whole to address this.
stress and health
6.52 We have already considered
two of the main comfort aspects of the aircraft cabin: the thermal
environment (paragraphs 5.37ff) and seating (paragraphs 6.33ff).
Before turning to the interaction between comfort and health,
we also briefly consider in-flight cabin noise.
6.53 There are no specific
regulatory requirements concerning cabin noise levels. Airbus
Industrie (p 165), British Airways (p 99) and Emirates (p 229)
indicated that cabin ambient noise was well below those levels
where passenger or crew health would be a source of concern.
6.54 Cabin noise arises from many sources: air passing
rapidly (at speeds approaching 600 miles per hour) over the aircraft;
the engines, transmitted through the aircraft structure and, particularly
behind the wings, through the surrounding air; ventilating air
passing through the inlet and outlet vents; in-flight entertainment;
conversation (perhaps louder than in normal surroundings given
the other noise); and other cabin activities.
6.55 It is difficult to see
how the principal causes of in-flight cabin noise, engine and
air noise, could be substantially reduced at reasonable cost.
Appreciation of this may explain why, other than from the
Royal College of Surgeons of Edinburgh (p 283) and Mr Sparks (Appendix
4), we received few representations that the levels should be
lower. However, earplugs are useful in reducing annoyance
from noise, particularly on overnight flights where passengers
are seeking to sleep. We understand that these are routinely offered
to first and business class passengers, and we recommend airlines
to extend the inexpensive courtesy of offering free earplugs to
6.56 That does not mean that
in-flight noise is not an issue - and it may be particularly so
in small aircraft. CAA mentioned noise and low frequency vibration
as something which may have adverse health effects (p 16) and
HSE identified noise as a particular matter meriting further research
6.57 BALPA made the point
on behalf of pilots that, although cockpit background noise is
within acceptable limits, the addition of radio communication
noise can cause the noise at the ear to exceed levels at which
hearing protection would be required by law if flight-decks were
not exempt from the Noise at Work Regulations (p 213).
As this may have both health and wider safety implications, we
recommend CAA and HSE to investigate the matter further.
6.58 We asked for views and
evidence about interactions between comfort, stress and health,
and discussed these with a number of our witnesses. It was generally
agreed that there was a complex relationship between them, and
that the air-travel experience as a whole had widely different
effects on individuals. As concisely summarised by Mr Smethers
of DETR (QQ 65-69) and the Public Health Minister (QQ 539 &
540), informed personal choice seems, as in many other areas,
to be the key.
6.59 Professors Moyle and Muir of Cranfield University
College of Aeronautics provided us with valuable material on environmental
and stress factors associated with air travel - and their singular
and additive impact on health and wellbeing - both in their evidence
(p 218), and in earlier research proposals that they had generated.
The Electro-Magnetism and Biocompatibility Association also provided
us with a very wide-ranging overview of the factors to be considered
when assessing the potentially adverse impact of the aircraft
cabin environment on crew and passenger health (p 226).
6.60 Our discussion of seating and space was largely
in connection with our principal concern with DVT, particularly
for already at-risk groups. We have some sympathy with the additional
concerns that discomfort and frustration from restrictive seating
and difficulties of moving about add to the general stress of
flying. It is widely perceived that discomfort and stress have
a negative impact on health and wellbeing. It is important to
note that stress is not just a mental state: it has physiological
consequences such as increased rates of heartbeat and breathing.
6.61 IAPA, AsMA, Dr Dawood and others expressed concern
that aircraft manufacturers, cabin designers, airline operators
and airport authorities pay little or no attention to these matters
(pp 243, 198 & 220, Annex 4). However, as Mr Smethers of DETR
indicated (Q 68), stress is a personal matter, and airlines and
their customers each have to make commercial choices in trying
to achieve a balance between what is desirable and the cost involved.
6.62 The most commonly quoted
of many factors associated with stress and air travel are listed
in Box 5, and we emphasise that these include pre-flight activities.
It is important to note that few of these factors are likely to
be experienced in isolation, and effects on individuals may be
compounded by multiple interactions. In our view, some of these
factors, particularly in combination, may well give rise to the
feelings of general malaise which people often attribute to poor
quality cabin air. Even if such factors do not give rise to illness
itself, they may cause detriment to the condition of the ailing
Factors associated with stress and air travel
General preparations for travel.
Journey, which may include feeder flight, to the airport.
Airport tumult: transport; managing luggage; queues for check-in; crowded waiting, refreshment and toilet facilities; getting to the gate or bussing to the aircraft, ground delays at gate and on apron; fumes.
Aircraft constraints: family separation; seating discomfort; mobility limitations; inadequate baggage stowage; perceived inadequate toilet facilities.
Cabin environment: low humidity; inability to control thermal conditions; vibration and noise.
Cabin environment: low pressure and low oxygen as potential augmentors for other factors.
Turbulence in flight.
Duration of flight without stops.
Flight and airport changes during journey.
Time-zone changes, fatigue, and inability to sleep.
Excessive alcohol consumption.
Fear of flying.
Anxiety about unfamiliar airport or procedures.
Flight cancellations and delays.
Regimentation, boredom, and loss of personal control.
For smokers, enforced non-smoking.
Concerns about destination, immigration control, baggage, and connecting flights or other onward travel.
Principal Sources: Aerospace Medical Association (p 198), BAE Systems (p 200), Cranfield University (p 218), Royal College of Nursing (p 277), individual cases in Appendix 4
6.63 We have become increasingly
aware of the unique nature of the aircraft cabin environment,
and of air travel itself, in terms of their potential impact on
the health and wellbeing of passengers and crew. Noting the
inter-relationship between comfort and stress and health, together
with the scope for combined adverse effect with other environmental
factors, we recommend that, when investigations are conducted
into the impact of any particular environmental factor on health
or wellbeing, the possibility of combined effects be given appropriate
attention. Putting this the other way round, we agree with
AsMA (p 198) that it is very unlikely that any ailment alleged
to be due to the cabin environment would be found to be caused
by a single factor, and that measures intended to alleviate a
given health concern must take into account the interaction of
a number of environmental factors.
6.64 A particular example
of where combined effects appear to be at work is jet-lag. We
received extensive evidence on this from Inflight Research Services
(IRS - p 240) and the Research Institute for Sport and Exercise
Sciences (RISES - p 269). It seems clear that the malaise of jet-lag
is more than the result of crossing time zones about which, of
course, nothing can be done. IRS notes particularly that the severity
of jet-lag is connected with the relative discomfort of the flight.
RISES made the point, reinforced by Professor Denison (p 94) and
Boeing (p 204), that jet-lag was not a minor matter. It may have
serious effects on judgement and impair performance. Boeing also
pointed out that it may not be possible for frequent international
travellers or long-haul flight crew to become acclimatised to
jet-lag (p 204).
6.65 RISES indicated that
enough was known about jet-lag for simple helpful information
to be given to travellers and also thought that the general arrangements
regarding in-flight entertainment and meals should take more note
of scientific knowledge in this area. We agree with RISES and
recommend airlines to review their arrangements for the timing
of refreshments and sleep periods on long-haul flights with jet-lag
in mind, and also to advise passengers both at booking and in-flight
about appropriate measures to deal with the effects.
86 Those travelling the longer distances are known
as ultra-long-haul. Back
We incline to the view of IAPA that technical and environmental
considerations are likely to stand in the way of developments
in supersonic and sub-orbital travel (p 243). Back
We understand that the UK is unique in actually specifying a minimum
measurement in this context. Back
Are you sitting comfortably?, Holiday Which?, Spring 2000. Back
Although not always using this term in the strict sense defined
in paragraph 6.38. Back
We have received no direct evidence on psychiatric matters. However,
it is not difficult to envisage flight stress factors triggering
or augmenting abnormal psychiatric states. Back