xstart=-20; 
xmax=11; % It works.
A=chebop([xstart,xmax]);
x=chebfun('x',[xstart,xmax]);
A.op= @(x,y) diff(y,2)-x*y;
% N[AiryAi[-20],30]  -0.176406127077984689590192292219
% 
A.lbc= @(y) [y-(-0.176406127077984689590192292219)];
A.rbc= @(y) [y-4.22627586496035959129883545080*10^(-12)];
S = A\0;
xlim auto; plot(S,'.-')