You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: air_density.m
    path of file: ./repos/CDT/cdt
    
    the code of the file until where you have to start completion: function rho = air_density(h)
% air_density computes density the baromometric forumula for a US Standard Atmosphere. 
% 
%% Syntax
% 
%  rho = air_density(h)
% 

    
function rho = air_density(h)
% air_density computes density the baromometric forumula for a US Standard Atmosphere. 
% 
%% Syntax
% 
%  rho = air_density(h)
% 
%% Description
%
% rho = air_density(h) returns the atmospheric density rho in kg/m^3 corresponding to
% the heights h in geometric meters above sea level.
% 
%% Examples 
% For examples, type 
% 
%  cdt air_density
% 
%% Reference
% The barometric formula uses a 7 layer formula (8 layers if you include
% invalid heights above 86 km) for the 1976 US Standard Atmosphere. 
% https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770009539_1977009539.pdf
% updated link: https://www.ngdc.noaa.gov/stp/space-weather/online-publications/miscellaneous/us-standard-atmosphere-1976/us-standard-atmosphere_st76-1562_noaa.pdf 
% 
%% Author Info 
% This function was written by Chad A. Greene of the University of Texas at
% Austin, 2018. 
% 
% See also air_pressure.

%% Error checks: 

if any(h>86e3)
   warning('Returning NaNs for altitudes greater than 86 km.')
end