Text in force at 29-59: from 29-12, effective 1 Feb 1977.
The main passenger aisle width between seats must equal or exceed the values in the following table: Passenger seating capacity Minimum main passenger aisle width Less than 25 inches from floor 25 inches and more from floor Inches Inches 10 or less------------------------------------------------------- 12[*] [15] 11 through 19-------------------------------------------------- 12 20 20 or more------------------------------------------------------ 15 20 [*A narrow width not less than 9 inches may be approved when substantiated by tests found necessary by the Administrator.]
41 FR 55472 · Source