In fact, FedEx likes to buy out Boeing facilities so that they're not "completely reliant" on Boeing for anything.[1]
As for the more general cloud v. on-prem debate, I usually don't like analogies, but the plane analogy is good because jets and logistics-management systems are two things that FedEx needs to handle extremely well to compete.
So, what does FedEx actually do wrt jets?
FedEx both owns and leases them. It mostly owns them outright. Its owned jets are a mix of new-ish to very old (think DC-9s). It also leases and some financing magic (such as some big lease agreements for new 777s a couple years ago).
The reason is that FedEx generally gets excess value from owning rather than leasing, but there are some circumstances where leasing makes sense.
Same goes for "cloud" deployments. The correct answers to cloud "versus" on prem for large organizations like FedEx - "it depends," "that's a false dichotomy," and "it's almost certainly a mix of both" - are neither interesting nor simple, and so those answers don't get execs' attention...or headlines.
For FedEx to brag about taking an extreme position on cloud deployment is breathtakingly foolish. If I were an investor, I'd want to hear something like, "Based on a careful analysis, we've decided to shift certain specific operations to cloud-based systems. We plan to maintain control over the infrastructure and operations of mission-critical systems that have demonstrated resilience." (I'm assuming the latter are systems like the financial institutions rely on, where purpose-built stuff like mainframes using IMS have demonstrated near-zero downtime and darn-near-bug-free software for decades, because FedEx, like banks, needs to handle lots of simultaneous transactions in real time without error or deadlock.)
[1] Example: https://www.ch-aviation.com/portal/news/102874-fedex-to-take...