The ovens are definitely בני יומם.
I didn't bother going back to track every step of this conversation, but I was basing this off the initial posting of the interview with Rabbi Elefant, and PG's comment on that interview. Rabbi Elefant made no mention of the ovens being a problem, only the plates/silverware. I assume even the non-mehadrin business meals are always supposed to be warmed up double-wrapped.
Why? Where are the keilim on the plane coming from? Commercial kitchens. Besides, the question was one of scale. PG asserted that El Al's scale was SO LARGE that it ensured that the keilim are not bnei yoman. I'm saying the bigger the scale, the bigger chance they are bnei yoman.
"You have stacks and stacks of plates, and the ones on top get used, come back to the kitchen, get washed, and get placed ON TOP of the stacks to be used again." In an airline catering setting, stuff gets washed and packed for transport, not washed and sent out to the customers setting. Those containers that are packed for transport are not like your stacks of plates analogy. I'm not opining on whether stam keilim is applicable there, just that the metzius is likely different than your standard commercial kitchen, say in a wedding hall.