Everyone responding saying it doesn’t happen is wrong. It may not happen often to them. I have flown 500,000 miles.

I have family and friends in the industry who pilot, work ground ops, maintenance, and are flight attendants. At an airline with over 300 departures per day things go wrong, crews time out, aircraft have issues on landing that somehow get ignored until morning, and many more examples then planes get swapped.

They generally have very few planes on standby because it’s like flying them empty, it’s an inefficient use of money. It turns into wack a mole quickly and one flight steals a plane, gate, or crew from another until none are left.