As I posted in another thread, our January/February J&E flights are in limbo- one leg doesn't exist any more even though nothing is amiss in "MyDelta". When I called Delta almost a month ago a rep said they were working on it. I have been tracking their progress (and also the evolution of flights on American) by doing partial bookings- needless to say it sure has been interesting.
In the case of Delta, the leg flown by Air France from Paris to Amman went away. Then it was changed to Transavia, but that went away because Transavia didn't fly on that date. Then they didn't fly from Paris but changed to Amsterdam (Transavia has separate Air France and KLM branches). Now, the Transavia's schedule doesn't show any flights to Amman from either! Of course, "My Delta" has not shown any of this!!
I have also been following American- they looked good at first, but prices are jumping all around and itineraries changing almost daily- initially, the first homeward bound legs available went from Cairo to Paris, then Cairo to Rome , and recently Cairo to Heathrow on BA has been added- and even more recently Cairo to Casablanca (and on to JFK) on Royal Air Moroc (joined Oneworld this year). The AA Business fares have now quadrupled! UPDATE: fares are now back to normal?!?!?!?
I guess I'll just sit tight for awhile, first to see what Tauck eventually does, then deal with Delta since I'm already booked, even though what they are showing doesn't exist! The fare was good when I booked. 
Between revenue and COVID issues and the unknown, I suspect this situation is happening with all airlines and could affect you whether you booked air with Tauck or directly.