Originally Posted by Often1

OP asks whether it is illegal. The answer is "yes" (at least in the US). But, there is close to zero likelihood that you would be prosecuted for wire fraud, which is what this is.

It does violate the COC and that may have longer term downsides if you ever also engage in hidden-city ticketing, need a quick & easy gate pass and so on

Consider whether just buying a sandwich or better isn't a bit easier and less sleazy?