Your "hail Mary hot takes" could be the answer. Or it could be business as usual.
The 717s are going to require a good chunk of cash if kept. About the cost of 5 A221s...
Hail-mary #1 seems the more probable to me. Maybe Boeing could place a few 717s with QF or HA but it wouldn't begin
to cover a meaningful fraction of the 88 leased frames.
Five A220s don't replace 91 717s. I expect DL (and everybody else major in the U.S. market, even WN) to be capital constrained for the next ~5 years. The idea of A320s subbing for 717s is interesting. How do those compare on trip costs?
A319 might be able to sub in for the 717 with frequency changes, combined with RJs. Could probably use Buses to replace the 717 capacity for a bit, and regrow with A220s on the upswing. You ditch a niche fleet that likely brings unique costs, and bring in a consolidation down to a core of 4 NB fleets until 2030 or so. 40 something 717s won’t be a fleet long for this world. It’ll either grow up from there, or head down to zero IMHO. My guess is things stay the same for the next two years, with maybe whatever deliveries can’t be deferred slowly replacing the old and unused fleets.
I think what makes DL's so interesting to discuss is their strategy of holding onto obsolete aircraft allows them an amazing flexibility in their going forward decision. A decision, I personally believe, that should be held off as long as possible as the terms for DL must be improving. Due to the lead time for seats or inducting new aircraft, I believe DL will decide on the fate of the 717 by end of 1Q2020, at the latest end 1H2020. That doesn't mean it will be public. This is my estimate on, in this down economy with 'hungry' vendors, how quickly DL could either get seats or a new fleet.
DL could buy used A320CEOs or 737NG. Pricing for those will improve post MAX return to service. So wait. Airlines have just started returning narrowbodies to the leasing companies. I believe there will be quite a few coming up, in particular from Indian airlines committed to NEO or MAX orders.
The airframes would also like orders. We discuss Boeing, but the reality is, Airbus is overproducing the NEO. Their customers want relief. At this time, the NEO slots could easily be freed up if DL wanted to buy and the two sides could come to terms. Or Airbus could deliver A220s. Eventually DL will start receiving them and a larger backlog would help the type. I also wouldn't rule out the E2-195 as a 717 replacement (DL is the master on low cost introduction of new fleets).
Since Delta could do just about anything for the 717 replacement (including refurbish these low utilization aircraft), we'll have to wait. The Delta executives must wait as pricing must be improving with time. With so many options, Delta should put out feelers and negotiate, then negotiate again, and keep on negotiating.
I've been thinking of the CAPEX on new seats, it will be lower in this environment. The vendors must be begging for more business.
So we can debate here quite a bit, but it will be the numbers, in particular cash burn, that determines if:
1. 717s are parked (as WN did for a while)
2. 717s receive new seats
3. Used A320CEO or 737NG fill the capacity (there will be plenty)
4. Or order new A220/A320NEO/MAX/E2-195 as the replacement.
I wouldn't want to be negotiating against DL. They will do something and have absolutely nothing to lose, for they could shrink more.
Of course, if not a GTF, BR700, or CFM-56, engine service contracts would need to be discussed.
For used aircraft pricing, see the aircraft lease values thread (the older one has many links on how used aircraft values have fallen):viewtopic.php?t=1449067viewtopic.php?f=3&t=1440991
Aircraft are still being produced and zero new aircraft are required for growth. So unless every new delivered aircraft results in a scrapping of an older aircraft, the market will need until a minimum 2023 to have used aircraft sell at a more traditional price (fraction of new based off wear and tear). So the next say 15 months is the best time for an airline to negotiate.
Winter is coming.