This (jacking up prices at busier times or, wink-wink, dropping prices at slower times) only works if the other big FF business do the same. If Delta was doing it but American was not, Delta would lose business to American. Someone else mentioned the limited supply of airline seats being a factor - and it is - but the fact that the whole industry jumped on board is a necessary condition for success.
It sounds like a classic "trial-balloon". If others quickly follow suit, they would change the industry. If the others don't, Wendy's is right back where they started - albeit with a bit of a PR mess.
IMO, a lot of this gouging behavior comes from the necessity of public companies to continue to grow - either top or bottom line, preferably both. In "retail", upping the numbers requires continuing to add stores, increasing same-store sales, reducing costs, and/or raising prices. Wendy's restaurants have to have pretty well saturated their market. Increasing sales is hard once a store is "mature" as it means winning competitive sales. Reducing costs gets harder over time. But supply chain issues, rising personnel costs, and inflation have provided perfect foils for price increases well beyond what's needed. If companies didn't have to grow to keep share prices rising (despite their markets not supporting growth), many could have nicely profitable, stable businesses. Instead, they try crap like this where it becomes abundantly clear to everyone that they're just trying to squeeze every last dollar out of you.