How often are aircraft delivery schedules amended?

When a new aircraft order is announced we enter a delivery schedule based on the best available information at the time. This may be estimated if no information is forthcoming from the airframe OEMs or the customer.

Our delivery schedules are constantly being reviewed and amendments made when:

1. New information comes to light on a particular customer order, for example a single update moving the delivery schedule out by 6-12 months, or there are several announcements over the year (such as type swaps and engine swaps). The delivery schedule is then updated according to the information provided by the source.
   
   
2. When the delivery schedule for a particular customer or a type is starting to 'bunch-up'. In these instances we look back historically, compare the delivery rates, and amend the backlog to match.

So the velocity in the amendment of delivery schedules depends upon the manufacturing performance of the airframe OEMs (build rates and customer handovers), and also the changing demand of customers, but generally there isn’t a great variance in what we forecast versus reality.