Explainer: How Aircraft Orders, Backlog and Book-to-Bill Ratios Differ and How to Read Them

BizJet Journal founder and editor Joash Koech has published an analysis of three measures that recur in business aviation market reporting: aircraft orders, backlog and book-to-bill ratios. An order is business accepted under a manufacturer's stated criteria; backlog is qualifying business still to be completed; and a book-to-bill ratio compares incoming orders with outgoing deliveries or revenue over the same period. Manufacturers do not necessarily define all three measures in the same way.

On orders, the analysis separates firm purchase agreements from options, letters of intent and reservations, which represent different levels of commitment. An announcement of "up to 100 aircraft" may combine a smaller firm commitment with optional aircraft, so reporting it as 100 firm orders would erase that distinction. Deposits may be refundable or non-refundable under particular conditions, and development programmes may collect expressions of interest while certification and delivery schedules remain unresolved.

Backlog is described as qualifying work remaining under a company's reporting policy, reportable in aircraft units, monetary value or both. General Dynamics' 2025 results disclosure distinguishes backlog from estimated potential contract value that includes items such as unexercised options, and combining those categories into one "firm aircraft order book" would misrepresent that disclosure. Backlog gives visibility into future work but not certainty, since contracts, financing, programme schedules and supplier constraints can change.

Gross orders are recorded before relevant cancellations or adjustments, while net orders account for them. In the analysis's fictional example ledger, opening backlog of 300 aircraft plus 140 new firm orders, less 20 cancellations (120 net orders) and 100 deliveries, gives a closing backlog of 320 before any other adjustments. Conversions between models, acquisitions and currency or contract changes can also affect reported figures.

A unit-based book-to-bill ratio divides aircraft orders by aircraft deliveries for the same period; in the example, 120 net orders over 100 deliveries gives 1.2, which does not imply a 20% rise in revenue or profit. Bombardier's full-year 2025 results explicitly reported a unit book-to-bill ratio of 1.4. A value-based ratio compares the monetary amount of bookings with the relevant billings or revenue measure as defined by the company, and cannot be obtained by dividing an aircraft count by a dollar amount.

Dividing backlog by annual production does not give a buyer's waiting time, because capacity is allocated by model, factory and delivery schedule, and backlog can span several years.

The analysis recommends aligning reporting periods, checking whether a ratio is unit- or value-based and whether orders are gross or net, and reading issuers' footnotes and revisions. The GAMA shipment series offers an independent view of delivered output, but it should not be used to infer a missing bookings figure.

Order and backlog headlines in business aviation are only as comparable as the definitions behind them. A figure that counts options or letters of intent beside firm contracts describes a different order book from one that counts firm business alone, and the General Dynamics disclosure shows a manufacturer itself drawing that line between backlog and estimated potential contract value. Comparing two companies' totals without checking those definitions can make one look stronger than the other for reasons that have nothing to do with demand.

A book-to-bill ratio above one says defined incoming business exceeded the defined outgoing measure in that period, and nothing more. Unit and value ratios answer different questions, and a 1.2 in the example ledger is a statement about aircraft counts, not about revenue or profit. Because capacity is allocated model by model and factory by factory, backlog read against annual production is a poor guide to when any individual buyer would take delivery.

The practical test for any new set of results is whether the period, the unit-or-value basis and the gross-or-net treatment match across the figures being compared, and whether later revisions or footnotes change the picture. GAMA's shipment series provides a separate check on delivered output.