Missing delays?

The last exercise showed you that there are columns in flights containing missing values. The result of the describe() function is below. You don't care too much about missing values in most columns, but missing values in the departure_delay column are problematic - that's one of the main columns you want to study.

Row variable             nmissing
    Symbol                 Int64
__________________________________
1   year                 0
2   month                0
3   day                  0
4   day_of_week          0
5   airline              0
6   flight_number        4
7   origin_airport       0
8   destination_airport  3
9   scheduled_departure  7
10  departure_time       3
11  departure_delay      56
12  scheduled_time       0

The DataFrames package and flights dataset have been loaded for you.