Originally Posted by
mersk862
First Class meals are your typical normal domestic first class hot meal (pasta/chicken for lunch/dinner).
You can order a special meal if confirmed in F more than 24 hours out.
I thought it was 6 hours except for AVML and KSML, but
this page says 12 except for KSML. In practice, if you upgrade at the FO window or don't buy a walkup ticket you can get a request in.