When Should a Launch Plan Switch to Its Backup?

A launch plan depends on one supplier delivering a critical component. A backup route exists, but it costs more and may narrow the first release.

If the supplier’s timing becomes uncertain, what should trigger the switch: a missed milestone, evidence that recovery is unlikely, or the cost of waiting? And who should own that trade-off, with whom consulted before the team commits?

Deciding the trigger in advance could make a contingency plan usable without turning every delay into a crisis. Where would you draw the line?