diff --git a/transform.Rmd b/transform.Rmd
index ce142ee..3193d91 100644
--- a/transform.Rmd
+++ b/transform.Rmd
@@ -813,6 +813,9 @@ daily %>%
     
     Which is more important: arrival delay or departure delay?
 
+1.  Our definition of cancelled flights (`!is.na(dep_delay) & !is.na(arr_delay)`
+    ) is slightly sup-optimal. Why? Which is the most important column?
+
 1.  Look at the number of cancelled flights per day. Is there a pattern?
     Is the proportion of cancelled flights related to the average delay?