Airborne is adding the "F" (and other codes?) to the beginning of the barcode to tell their system what type of delivery it is. This character is actually in the barcode data, even though it is not visible in the human-readable caption. If this interferes with your operations and you really want to strip it out, you will need an ADF-capable scanner.
All current model Wasp scanners with the exception of the WCS3900 series and WWR2900 series are able to do ADF programming. Please check http://www.waspbarcode.com/scanners/ or contact Wasp sales at 866-547-9277 option 1 for purchase information, or support at 866-547-9277 option 2 for programming assistance.