Noun
wingspread (plural wingspreads)
The distance between the extreme tips of the wings of a bird, insect or aircraft.
Sign *89 is not listed in Ventris & Chadwick's (1973) tables but it does appear in the appendix of Bennett (1964) as part of the Wingspread convention. Source: Internet
In recent times, CIPEM inherited the former authority of Bennett and the Wingspread Convention in deciding what signs are "confirmed" and how to officially represent the various sign categories. Source: Internet