I think it's funny, not offensive.

I think a majority (not all) of passengers would also think it was funny.

I think a lot (perhaps a majority, but not all) of crew members would think it was funny.

I think If this T-shirt attacked people ("UA flight attendants never effing work."), that would be different. The TSA shirt cited in a post above is gross because it's attacking people. But this is just making a sardonic comment on something that almost everyone here agrees is a genuine problem.

I think it's stunning that something this minor has garnered over 150 posts.