Commercial airliners

An airliner is a transport category airplane, certificated under Part 25, which prescribes the airworthiness standards for the issue of a type certificate and for changes to it.¹ That single fact draws the boundary for this category. A large business jet is usually certificated to the same part and sits in the business jets guide because of what it is sold to do, not because the rulebook is different. A freighter conversion is not a new airplane and belongs with the modification houses.

The type design and the route are two different approvals

Part 25 covers the airplane. It does not, by itself, let you fly the route you bought it for. Extended operations have a design side, which Part 25 addresses in its special provisions for ETOPS type design approvals, and an operating side.¹ On the operating side, no certificate holder may fly a turbine-powered airplane past 60 minutes from an adequate airport with two engines, or past 180 minutes with more than two on a passenger flight, unless the operation is approved under the rule's own appendix and written into the operations specifications.² So a fleet decision has three questions, not one: what the type design is approved for, what your certificate is authorised for, and how long the second takes when the first is already done.

What separates one airframe from another on a spreadsheet

Ask for guaranteed figures, not brochure figures: payload at range on your sectors, fuel burn at your typical cruise, maximum takeoff weight variants and what a weight increase costs later. Ask which engine options exist, what each does to maintenance cost per hour, and whether the engine is bought from the airframer or contracted separately. Ask for the maintenance programme the type was certificated with, the check intervals, and what the first heavy check is expected to consume. Ask about delivery: the position, the escalation formula, the specification freeze date and what a change after freeze costs. Every one of those is a number a manufacturer already knows.

Where the public record can be checked

The FAA publishes its design approvals, so the type certificate, its data sheet and the supplemental type certificates written against the type are all public and searchable.⁴ That record proves what has been approved and by whom. It does not price anything, it does not tell you what a delivery slot is worth, and it says nothing about the seller's schedule performance. Airworthiness directives fill in the fleet's history. An AD is a legally enforceable rule the FAA issues when an unsafe condition exists in a product and is likely to exist or develop in others of the same type design.³ Read the directives against the type and against the engine before the fleet meeting, and read the terminating actions with them, because who paid for compliance last time is a fair question to put to a seller.

Questions to ask before shortlisting

Ask which model in the family your mission actually needs, and what the next model up costs per seat. Ask what the residual value assumption in the pitch is, and whose forecast it came from. Ask which support is in the aircraft price and which is a separate agreement. Ask what your own certificate needs to add before the first revenue flight, and how long the manufacturer says that has taken for comparable operators.

The companies below are listed on public facts, each with its source linked.