ONE missing was an Acceptable Defect but TWO was not - never understood that. Probably hadn't been considered, researched, demonstrated and certificated on the basis that to lose one winglet may be regarded as a misfortune; to lose both looks like carelessness - Basil
A historical precedent, admittedly in respect of a different form of travel, may be found here
https://www.youtube.com/watch?v=RghKdGn8h5A 
Jack