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  • BSI Flex 1903 v2:2024-06 community preview

    This is an interactive version 2 of BSI Flex 1903. The aim of the standard is to create a lexicon of standard terms and acronyms used in this sector. Please note, content is still undergoing internal review and there may be minor changes at full publication.

    We welcome your engagement and comments on this version to help inform the development of the standard. We would also welcome general feedback including what terms could be considered for future versions and these can be made through our dedicated feedback page .

atypical air environment (AAE)



  • Definition

    specified volume of airspace where the potential for an otherwise unmitigated encounter with crewed aircraft meets an acceptable level


    NOTE 1 Examples of AAE described in UK CAA CAP 2968, Consultation: Unmanned aircraft operations within an atypical air environment [11], include:

    • within 30 m (100 feet) of any building or structure;

    • within 15 m (50 feet) of a permanent linear structure, e.g. a railway, road or powerline; and

    • within the confines of private property at a height not exceeding 15 m (50 feet), e.g. an industrial site where security personnel use a UA for perimeter inspection.

    NOTE 2 Atypical air environments exist within segregated and non-segregated airspace; the main purpose of their identification is to facilitate beyond visual line of sight (BVLOS) (3.1.35) operations in non-segregated airspace.


    Previous Version: 1.0 Release date: September 2023 

    volumes of airspace where crewed aircraft do not routinely fly and the likelihood of an otherwise unmitigated encounter with a crewed aircraft is reduced to an acceptable level

    NOTE 1 Examples include airspace near manmade structures such as buildings or high voltage powerlines, or at altitudes above those achievable by most crewed civil aircraft.

    NOTE 2 Atypical air environments might exist within segregated or non-segregated airspace, however the main purpose of their identification is to facilitate BVLOS operations in non-segregated airspace.

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