Alliance, Atlas are technically wet leased, they wet leased a few AN jets for a period of time after the AN collapse. At the same time they had a similar deal with Air Canada for some 767s for a few months.
It also looks like they wet leased passenger jumbo in the late 80s from
Aer Lingus and Martinair in addition to Tower Air. To cover capacity shortfalls according to the thread.
So temporary wet leasing is not uncommon or new, but will ruffle some feathers no doubt.