FAA Federal Aviation Regulations (FARS, 14 CFR)

The passenger aisle width at any point between seats must equal or exceed the values in the following table:

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Minimum passenger
aisle width (inches)
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Passenger seating capacity            Less than   25 in. and
25 in.     more from
from floor     floor
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10 or less..............................  \1\ 12          15
11 through 19...........................      12          20
20 or more..............................      15          20
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\1\ A narrower width not less than 9 inches may be approved when
substantiated by tests found necessary by the Administrator.

[Amdt. 25-15, 32 FR 13265, Sept. 20, 1967, as amended by Amdt. 25-38, 41 FR 55466, Dec. 20, 1976]