Range from Full dE/dx for 5.5MeV alpha using Geant4 10.7.2
Air is identical composition and density as G4_Air
Air Original is Air composition (N, O only, density 1.29 mg/cm3) from original source code of TestEm0
default EM physics is emstandard_opt0 (in PhysicsList.cc)
SRIM Results are from Ziegler et al.'s SRIM-2008.04 program (http://www.srim.org/)

EM Physics List        Air Original      Air               G4_AIR
                       N,O 1.29 mg/cm3                     1.20479g/cm3

emstandard_opt0        3.68108 cm        3.93544 cm        3.93341 cm
emstandard_opt1        ---               3.93544 cm        3.93341 cm
emstandard_opt2        ---               3.93544 cm        3.93341 cm
emstandard_opt3        ---               3.93479 cm        7.53253 mm
emstandard_opt4        ---               3.93479 cm        7.77762 mm
empenelope             ---               3.93479 cm        3.93238 cm
emlivermore            ---               3.93479 cm        3.93238 cm       

SRIM Program           3.864 cm          4.476 cm          4.476 cm