It depends on what the purpose was... I have actually suggested several times that AA would benefit from acquiring some used aircraft but that is not AA's style of working.
I just said it about the 77L which could allow AA to start JNB, a route that I have repeatedly said MIA is ideally located to serving.
Problem is that the 77L is the only aircraft that has been shown to be able to operate year round nonstop without restrictions to and from JNB-N. America. DL has the aircraft and is flying the route. Neither AA or UA have it.
Specific to this discussion, what so many people cannot understand is that the metric is not whether the plane will be a 15-20 year metric which is the standard that any airline has to make if they are buying new but whether the 346s can be profitably used for as little as 5-7 years in the fleet. Given that the 346 can easily be used to providing upgrades of some existing 77E/77L routes, allowing the 777s to be redeployed to new routes and THEN used to replace 744s, which DL knows are ending the end of their lives within the next few years.
The 346 burns significantly less fuel than the 744 and is only a bit smaller in total seating size than the 744, but given that DL has already said that it wants to regauge its NRT hub, the 346 could be coming along at just the right time to allow DL to pull the 744s from NRT while adding new capacity to China, where DL said it is seeing very positive results (and where DL now has the highest average fares from the US to PVG, a title held by UA for years).
Airbus keeps the 340 flying for a few more years instead of parking them while Rolls-Royce gets a little bit more of DL's business, important since DL now has Rolls or Rolls related engines on perhaps more of its fleet than any other airline in the Americas thanks to the 717 and M90 deals on top of the handful of 777ERs. With an RFP for a number of widebodies outstanding, Rolls could use any advantage in that deal they can get.
If AA came up with the same justifications, it could be equally as compelling.