[Slicksadick]

I believe commercial aircraft are required to have at least a 12:1 glide ratio.

[Slicksadick]

The ratio L/D is sometimes called glide number, or glide ratio, or finesse.
Boeing B707-320 19.4
Douglas DC-8 17.9
Airbus A320 17.
Boeing 767-200 19.
Boeing 747-100 17.7
Douglas DC-10 17.7
Lockeed Tristar L1011 17.0
Douglas DC-9 (1966) 16.5
Boeing B727-200 16.4
Fokker 50 (1966) 16
Douglas DC-3 (1935) 14.7
Ford Trimotor (1927) 12.
Wright Flyer I (1903) 8.3


Table 3: L/D of Some Birds Bird L/D
House Sparrow (passer domesticus) 4.
Herring Gull (larus argentatus ) 10.
Common Tern (sterna hirundo ) 12.
Albatross (diomeda exulans ) 20.