I would add Resourcing to the list. Have Delta airlines joined the mob of traditional big businesses who decide technology is expensive and send it to the cheapest possible?
Alternatively it could just be an catastrophic infrastructure failure.
Interesting! Are there any source listings anywhere? Do they have particular programming tools or methods that help them deal with the complexity? If it's all assembly, I'm surprised this is only happening now.
While I don't doubt their investment in their software stack to manage operations, Delta is hardly always on time nor consistent. I fly them 2-3 times a month and for the past two months (including today) every flight has has delayed (to and from destination) with only one being weather related.
Alternatively it could just be an catastrophic infrastructure failure.