system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When a multi-billion dollar transaction occurs between two companies, how are the funds transferred/managed?

For example, let's say that American Airlines buys 50 Boeing 787-8 for the price of 50*$211.8M = $10.59B. Does a staff member of AA log in their system, enters the amount, then click 'Transfer' to Boeing's bank account, or is it more complex? Are the funds transferred by gradual amounts or in a single package? Are there special security procedures AA and Boeing must follow? Where do the funds end up?
gpt
Typically by Wire Transfer.  

Wire Transfers, unlike checks or regular electronic bank payments (known as ACH transactions in the US), are irrevocable once final -- even in the case of fraud.  (That is, if someone authorized to make a wire transfer makes one, even if defrauded or illegally embezzling funds, the accountholder are still liable for the payment.  If someone at the bank who isn't authorized to make a wire transfer illegally makes one, the accountholder is not liable.)

The idea is that businesses need finality when they receive payments, they can't just have money disappear from their accounts like if a "chargeback" or "stop payment" is done.  If a wire transfer is made and you need your money back, you have to sue the recipient -- you can't just ask the bank to reverse the charge.  For transactions between businesses, it's assumed that the need for finality outweighs the fraud protections that checks and nonwire electronic payments provide.  (In the US, wire transfers are rarely used by consumers.  Also why scamsters try to get you to wire money to them - people wrongly assume that wire transfers have the same protections as consumer payment systems.)  Source: The Uniform Commercial Code Article 4A.