Even with 20 minute days, you get 60 RL hours between the announcement that a production line might close, and the announcement that it is closed. 2.5 days is plenty of time to order planes if you want them.
I suspect what was more of a problem is that the 6 month countdown started less than 18 months into the game, and the planes are very expensive, so those who ended up wanting to get them hadn't planned ahead in time, and simply didn't have the cash to order enough planes.
As for cancelling your existing leases being a little steep, how long did you originally lease them for? The discount for very long leases, especially from the used market, is almost never worth the loss of flexibility.