This part of ISO 7718 specifies minimum requirements for dimensions and unobstructed space around main-deck passenger doors of future types of civil-passenger transport aircraft when they are intended to be compatible with the thousands of passenger boarding bridges and passenger transfer vehicles existing, or being planned, in airports worldwide. This part of ISO 7718 is not applicable to existing models of civil transport aircraft, or derivative models with the same fuselage, for which the aircraft-mating section of passenger boarding bridges or passenger transfer vehicles is expected to be compatible with ISO 16004. This part of ISO 7718 is not intended to restrict in any way the basic design of any future types of civil-passenger transport aircraft. However, it aims to clarify for aircraft-design engineers the design characteristics that would make it difficult, or impossible, for a new type of aircraft to connect adequately with existing airport passenger boarding bridges or passenger transfer vehicles. If, on a future model, basic aircraft-design requirements impose certain dimensional characteristics that do not comply with this part of ISO 7718, one of the following will apply, and in each case, aircraft-handling constraints and operating costs will increase: - alternative methods of embarking/disembarking passengers (e.g. integral aircraft stairs) will need to be implemented; or - existing passenger boarding bridges and/or passenger transfer vehicles will need to be modified/reworked to some extent in the airports where this type of new aircraft will operate; or ? additional interface devices/equipment will be needed to connect this type of new aircraft with existing passenger boarding bridges and passenger transfer vehicles.