Gordon Wiggett kept a very detailed log of his B-17 sorties across the Channel during WWII. Each entry lists: first, the destination; second, the date; third, the number of air hours; fourth, the designation of 'sortie' for a succesfull mission, or 'abortive' or 'call back' for unsuccesfull missions. It's unclear what the running totals in the far right hand column designate.